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THE  CONNECTICUT 


AGRICULTURAL  EXPERIMENT  STATION 


NEW  HAVEN,  CONN. 


BULLETIN  167,  APRIL,  1911. 


INHERITANCE    IN    MAIZE. 


By  E.  M,  East  and  H.  K.  Hayes. 


The  Bulletins  of  this  Station  are  mailed  free  to  citizens  of  Connecticut 
who  apply  for  them,  and  to  others  as  far  as  the  limited  edition  permit. 


Comecticnt  Apicjltiral  Eiperlient  Station. 


OKF^ICERS    AND    STA.KF 


BOARD  OF  CONTROL. 

His  Excellency,  Simeon  E.  Baldwin,  Ex  Officio,  President. 

Prof.  H.  W.  Conn,    Vice  President Middletown. 

George  A.  Hopson,  Secretary Wallingford. 

E.  H.  Jenkins,  Director  and  Treasurer New  Haven. 

J.  W.  Alsop    ...       Avon. 

Charles  M.  Jarvis    .   .    .   .  • Berlin. 

Frank  H.  Stadtmueller Elmwood. 

James  H.  Webb Hamden. 


Administration 


STATION  STAFF. 
E.  H.  Jenkins,  Ph.  D',  Director  and  Treasurer. 
Miss  V.  E.  Cole,  Librarian  and  Stenographer. 
Miss  L.  M.  Brautlecht,  Bookkeeper  and  Stenographer. 


Chemistry. 

Analytical  Laboratory, 


John  Philips  Street,  M.  S.,  Chemist  in  Charge. 
E.  Monroe  Bailey,  Ph.  D.,  C.  B.  Morrison,  B.  S. 
R.  B.  Roe,  A.  B.,  C.  E.  Shepard,  Assistants. 
Hugo  Lange,  Laboratory  Helper. 
V.  L.  Churchill,  Sampling  Agent. 


Proteid  Research, 


T.  B.  Osborne,  Ph.  D.,  Chemist  in  Charge. 
Miss  E.  L.  Ferry,  A.  B.,  Assistant. 
Miss  Luva  Francis,  Stenographer. 


Botany. 


G.  P.  Clinton,  S.  Ti.,  Botanist. 

E.  M.  Stoddard,  B.  Agr.,  Assistant. 

Miss  M.  H.  Jagger,  Seed  Analyst. 

Miss  E.  B.  Whittlesey,  Herbarium  Assistant. 


Entomology. 


W.  E.  Britton,  Ph,  D.,  Entomologist;  also  State 

Entomologist 
B.  H.  Walden,  B.  Agr.,  D.  J.  Caffrey,  B.  Agr., 
A.  B.  Ch.amplain,  Assistants. 
Miss  E.  B.  Whittlesey,  Stenographer. 


Forestry. 


Samuel  N.  Spring,  M.  F.,  Forester;  also  State 

Forester  and  State  Forest  Fire  Warden 
W.  O.  FiLLEY,  Assistant. 
Miss  E.  L.  Avery,  Stenographer. 


Plant  Breeding. 


H.  K.  Hayes,  B.  S.,  Plant  Breeder. 
C.  D.  HUBBELL,  Assistant. 


Buildings  and  Grounds. 


William  Veitch,  In  Charge. 


TABLE  OF  CONTENTS. 


Introduction, 


Page. 
5 


PART  I. —  The  Material  and  the  Problem. 

The  Plant  and  its  Origin, 

The  Varieties  of  Maize,     .  . 

The  Problem  and  its  Treatment, 

Previous  Work  on  Inheritance  in  Maize, 

The  Material  used. 

Methods  used,         .... 

Experimental  Error, 


10 
14 
18 
21 
25 
28 
31 


PART  II. —  Endosperm  Characters. 


Inheritance  of  Starchiness, 

32 

Conclusions,             .             .             .       . 

43 

Inheritance  of  Yellow  Endosperm, 

46 

Conclusions, 

56 

Inheritance  of  Aleurone  Color,    . 

57 

Family  (24  x  54), 

59 

Family  (8  x  54), 

67 

Family  (15  x  54), 

74 

Family  (18  x  54), 

76 

Family  (7  x  54), 

80 

Family  (17  x  54), 

80 

Family  (19  x  54), 

81 

Family  (60  x  54), 

81 

Conclusions, 

90 

PART  III.— Xenia. 

General  Discussion  of  Zenia, 


101 


PART  IV.— Plant  Characters. 


Page. 


Podded  and  Podless  Maize , 

105 

Pericarp  Color,        .... 

105 

Cob  Color,                .... 

108 

Silk  Color,                 .... 

108 

Glume  Color,           .... 

109 

General  Discussion  of  Red  Sap  Color,    . 

109 

Physical  Transformations  of  Starchiness, 

110 

Size  Characters,      .... 

117 

Number  of  Rows  of  Seeds,    . 

120 

Heights  of  Plants, 

123 

Length  of  Ears, 

124 

Weight  of  Seeds, 

124 

PART  V. —  Plant  Abnormalities. 

Dwarf  Forms, 

Regularity  of  Rows  of  Seeds, 

Bifurcated  Ears,     . 

Ears  with  Lateral  Branches, 

Plants  with  Striped  Leaves, 

Hermaphrodite  Flowers, 


129 
131 
.132 
133- 
134 
134 


GpQeral  Conclusions, 
Literature  Cited, 


136 


13& 


INHERITANCE  IN    MAIZE. 


E.  M.  East  and  H.  K.  Hayes. 


INTRODUCTION. 


The  investigations  reported  in  this  paper  were  begun  in  the 
spring  of  the  year  1906.  During  the  first  four  years  the  work 
was  conducted  at  the  Connecticut  Agricultural  Experiment 
Station.  Since  the  fall  of  1909,  it  has  been  carried  on  both 
there  and  at  the  Bussey  Institution  of  Harvard  University. 
Strictly  speaking  the  researches  comprise  more  than  five  years' 
work,  for  several  of  the  pure  varieties  used  as  parent  stocks 
had  been  selfed  for  the  two  previous  years,  so  that  a  number 
of  crosses  were  made  in  1905  with  full  assurance  that  as  far  as 
most  of  the  visible  characters  were  concerned,  the  parent 
strains  were  pure.  There  was  some  further  advantage  gained 
in  that  the  writers  have  been  interested  in  experimental  maize 
breeding  since  1900,  for  without  this  experience  the  probable 
error  of  the  results  would  be  greatly  increased. 

Genetic  research  during  the  past  decade  has  been  very  fruit- 
ful of  results ;  nevertheless  one  could  scarcely  say  that  the  field 
has  been  thoroughly  surveyed,  much  less  that  any  part  of  it 
has  been  completely  investigated.  The  rediscovery  of  Mendel's 
law  in  1900  opened  up  a  new  era  in  the  search  for  the  principles 


*"  Contribution  from  the  Laboratory  of  Genetics,  Bussey  Institution 
of  Harvard  University,  No.  9." 


6  INHERITANCE  IN  MAIZE. 

of  heredity.  Mendel's  chief  discovery  —  segregation  of  poten- 
tial characters  in  the  germ-cells  of  hybrids  and  their  fortuitous 
recombination  —  was  one  of  the  really  great  achievements  in 
biology,  but  even  so,  it  may  be  questioned  whether  his  chief 
legacy  is  not  his  method  of  work.  As  has  already  been  stated 
by  Bateson,  previous  investigators  even  including  the  biometri- 
cians  dealt  with  facts  en  masse,  and  the  seeming  order  of  the 
mathematical  formulas  deduced  served  rather  to  conceal  than 
to  reveal  the  individual  facts.  Mendel's  method  of  individual 
analysis  by  the  study  of  simple  characters  in  carefully  con- 
trolled pedigree  cultures,  however,  has  yielded  and  will  continue 
to  yield  results  of  great  value  to  science.  Still,  since  we  are 
dealing,  as  yet,  with  the  simplest  elements  of  the  science  of 
genetics,  the  subject  matter  of  an  investigation  may  be  expected 
to  yield  results  (other  things  being  equal)  somewhat  in  the 
proportion  in  which  it  fulfills  the  following  technical  require- 
ments. 

1.  The  genus  or  species  under  investigation  should  be 
variable.  There  should  be  a  goodly  list  of  types  which  are 
differentiated  by  definite  characters  easy  of  determination. 
That  is,  the  differences  should  be  largely  qualitative  and  not 
quantitative. 

2.  The  different  types  should  be  freely  fertile  inter  se,  unless 
an  investigation  of  the  causes  of  sterility  is  contemplated. 

3.  The  flower  structure  should  be  such  that  the  technique 
of  crossing  and  selfing  is  simple  and  accurate. 

4.  Since  the  accuracy  of  an  analysis  of  the  manner  in  which 
characters  are  inherited  increases  —  generally  speaking  —  as 
the  square  root  of  the  number  involved,  the  subjects  should 
return  a  large  number  of  seed  per  operation  (selfing  or  crossing). 

5.  The  flowering  branches  should  be  numerous.  This  is 
necessary  for  three  reasons.  If  one  is  dealing  with  flower 
characters  he  must  be  able  to  determine  the  character  of  the 
plant  from  a  mature  flower  while  immature  blossoms  still 
remain  for  the  production  of  the  controlled  seed.  Obviously, 
it  is  also  an  advantage  when  dealing  with  plant  characters, 


INTRODUCTION.  7 

to  have  more  than  one  opportunity  to  secure  a  desired  union. 
Further,  it  is  advantageous  to  be  able  to  make  several  different 
crosses  upon  one  plant. 

6.  Seed  should  be  viable  for  several  years  in  order  that 
different  generations  may  be  compared  at  the  same  time.  This 
enables  one  to  reduce  to  a  minimum  the  physiological  fluctua- 
tion due  to  varying  environment  which  many  characters  undergo 
in  a  marked  degree. 

7.  The  subject  material  should  be  "workable"  cytologically 
in  order  that  it  may  be  attacked  from  both  standpoints. 

It  might  be  remarked  here  that  some  botanists  consider  that 
genetic  research  can  throw  no  new  light  upon  evolution  and  upon 
the  meaning  of  species,  unless  the  subject  material  is  an  unculti- 
vated genus  or  species.  This  criticism  is  apparently  no  more 
pertinent  than  the  one  the  chemists  had  to  meet  years  ago 
when  they  were  told  that  synthetic  compounds  could  not 
possibly  be  the  same  as  those  produced  by  nature.  The  fact 
of  physiological  fluctuation  due  to  varying  environment  is 
admitted,  but  it  is  not  admitted  that  the  mechanism  of  hereditary 
transmission  of  the  character  in  question  is  affected  by  these 
fluctuations. 

Some  idea  as  to  the  effectiveness  of  an  inquiry  concerning 
inheritance  in  maize  from  the  standpoint  of  science  may  be 
gained  then  by  examining  the  degree  in  which  the  plant  fulfils 
the  above  requirements. 

Although  the  forms  of  maize  are  regarded  by  botanists  as 
belonging  to  the  one  species  Zea  mays  L.,  there  is  probably  no 
species  of  the  flowering  plants  —  if  horticultural  color  varieties 
are  excepted  —  that  appears  under  such  varied  forms.  These 
forms  are  perfectly  fertile  inter  se,  moreover,  so  that  the  first 
and  second  of  our  requirements  are  fulfilled  perfectly.  The 
third  requirement,  that  of  an  easy  technique  and  accurate 
control  of  desired  matings,  is  met  very  imperfectly.  The 
plant  is  monoecious.  Ordinarily,  this  type  of  flowering  habit 
is  desirable  in  pedigree  culture  work  because  accidental  selflng 
is  usually  much  more  easy  to  prevent  than  it  is  in  hermaphroditic 
plants.     In  the  case  of  maize,  however,  there  is  such  an  enor- 


8  INHERITANCE  IN  MAIZE. 

mous  production  of  pollen  that  it  is  continually  present  in  the 
air  of  the  maize  field.  In  spite  of  all  precautions,  therefore, 
seeds  of  unknown  paternal  ancestry  do  creep  into  the  cultures. 
The  general  error  due  to  this  source  has  been  determined  in 
cases  which  are  described  later,  but  the  determination  of  a 
probable  error  in  a  mass  of  data  is  not  sufficient  in  genetic 
work.  An  actual  error  in  which  a  single  seed  of  unknown 
paternity  becomes  the  ancestor  of  a  pedigreed  line,  is  sufficient 
to  upset  all  inductions  drawn  from  the  data.  For  this  reason 
the  cultures  have  had  to  be  larger  than  would  otherwise  have 
been  necessary. 

The  requirement  of  a  large  number  of  seeds  from  one  union 
to  reduce  the  probable  error  of  chance  fertilization  among 
gametes  differing  in  character  is  quite  satisfactory  in  maize  as 
from  two  hundred  and  fifty  to  twelve  hundred  seeds  are  pro- 
duced on  the  cobs  of  the  various  races.  The  small  number  of 
flowering  branches,  however,  is  a  serious  objection.  In  some 
cases  there  are  two  or  even  three  and  four  ears  upon  each  plant ; 
but  in  most  cases,  especially  in  the  large  races,  there  is  but  one 
ear.  And  even  where  there  is  an  extra  ear  one  gains  but  little 
advantage.  The  ears  mature  about  the  same  time  and  it  is 
impossible  to  find  out  what  seed  characters  the  plant  possesses 
before  pollinating  the  ear  which  is  to  have  its  place  in  the  con- 
trolled culture.  The  disadvantage  of  this  fact  to  the  investi- 
gator is  apparent  if  one  remembers  that  when  studying  ear 
abnormalities  sometimes  twenty  to  twenty-five  cobs  must  be 
selfed  by  hand  to  be  reasonably  certain  that  one  selfed  ear 
with  the  desired  characters  is  obtained. 

Maize  seed  is  rather  delicate  and  must  be  carefully  dried  in 
a  place  where  there  is  a  good  circulation  of  air.  When  dried 
until  the  moisture  content  is  only  about  ten  per  cent,  it  remains 
in  fairly  good  condition  for  three  seasons.  Seed  older  than 
this  is  almost  worthless.  In  fact,  there  is  a  possibility  of 
obtaining  distorted  results  even  in  the  second  year.  Ninety- 
eight  to  one  hundred  per  cent  of  properly  dried  seed  should 
germinate  the  next  spring  after  harvesting,  but  this  percentage 
falls  to  about  ninety  the  year  following.  If,  therefore,  seeds 
of  any  particular  gametic  structure  should  lose  their  vitality 
first,  incorrect  results  would  be  obtained. 

The  chromosomes  of  maize  are  small  and  difficult  to  studv 


INTRODUCTION.  g 

and  scarcely  anything  is  known  of  their  behavior  during  the 
maturation  divisions. 

This  discussion  should  give  some  idea  of  the  advantages  and 
disadvantages  that  maize  presents  as  subject  material  for  a 
genetic  investigation  from  the  standpoint  of  pure  science.  The 
plant,  however,  even  if  not  as  perfect  as  some  others  from  this 
point  of  view,  has  another  claim  which  ought  not  to  be  "dis- 
regarded. The  fact  that  maize  is  the  basis  of  the  agricultural 
wealth  of  the  country  makes  it  eminently  desirable  that  every 
fact  about  the  inheritance  of  its  characters,  should  be  learned 
as  soon  as  possible.  It  is  only  through  the  application  of  such 
knowledge  that  the  present  arbitrary,  and,  in  a  way,  unscien- 
tific methods  of  its  improvement  as  an  economic  crop  will  be 
placed  upon  a  definite  and  orderly  basis. 


INHERITANCE  IN  MAIZE. 


PART  I. 

THE  MATERIAL  AND  THE  PROBLEM. 

The  Plant  and  its  Origin. 

Although  there  is  no  absolute  information  as  to  the  origin 
of  maize,  most  botanists  agree  that  its  original  home  is  Mexico 
(Harshberger  '93)  or  the  region  to  the  south  of  there.  As  to 
how  it  originated  there  has  been  much  speculation,  and  various 
views  are  held  by  different  writers.  We  think  it  not  out  of 
place  to  give  here  a  synopsis  of  the  most  important  theories, 
because  in  our  opinion,  the  results  from  the  pedigree  culture 
work  on  the  inheritance  of  plant  characters  described  in  Parts 
IV  and  V  throw  considerable  light  on  the  subject. 

The  Tribe  Mayde^  of  the  order  GramineEe  comprises  but 
seven  genera  and  only  sixteen  or  seventeen  species.  The  two 
genera  which  interest  the  maize  student  are  Zea  and  Euchlsena 
both  of  which  are  monotypic.  The  especial  distinctions  be- 
tween the  two  are  given  by  Lamson-Scribner  (  :  00)  in  his  key 
to  the  genera  of  Maydese  as  follows : 

"Euchlaena,  pistillate  spikes  axillary  fasciculate,  distinct, 
axis  of  each  articulate." 

"Zea,  pistillate  spikes  axillary,  grown  together,  forming  a 
compound  spike  with  a  much  thickened,  continuous  axis." 

His  complete  descriptions  are: 

''EuchlcBua  Schrad.  Ind.  Sem.  Hort.  Goett.  1832.  Spikelets 
unisexual,  monoecious;  the  staminate  2-fiowered,  in  pairs, 
one  sessile  the  other  pedicellate,  arranged  in  terminal  paniculate 
racemes;  the  pistillate  1-fiowered,  sessile  and  solitary  at  each 
joint  of  an  obliquely  articulate  rhacis  of  a  simple  spike;  the 
spikes  fasciculate  in  the  leaf  axils  and  each  more  or  less  enveloped 
by  a  foliaceous  bract.  Glumes  in  the  staminate  spikelets  4, 
acute,  the  first  two  membranaceous,  empty;  flowering  glumes 
smaller  and  like  their  paleas,  hyaline.  Stamens  3.  Glumes  of 
the  pistillate  spikelets  4,  the  outer  one  broad  and  boat-shaped, 
smooth,  soon  becoming  hard,  surrounding  the  inner  glumes  and 


ORIGIN  OF  THE  PLANT.  ii 

narrow  rhacis,  second  glume  empty  coriaceous,  third  glume 
hyaline  with  a  palea  but  no  flower;  fourth  or  flowering  glume 
with  its  palea  hyaline.  Styles  very  long,  filiform,  shortly  bifid 
at  the  apex. 

Tall  annuals  with  long  and  broad  leaves,  closely  resembling 
Indian  corn  in  habit.  Species  one  with  several  varieties  in 
Mexico  and  Central  America." 

''Zea  Linn.  Sp.  PI.  971.  1753.  Spikelets  unisexual,  mon- 
oecious; the  staminate  2-fiowered  in  pairs,  one  sessile  the  other 
pedicellate,  along  the  numerous  branches  of  a  terminal  panicle; 
the  pistillate  1-fiowered,  sessile,  crowded  in  several  rows,  along 
a  much  thickened  continuous  axis  arising  from  the  lower  leaf- 
axils  and  closely  enveloped  by  numerous  large  foliaceous  bracts. 
Glumes  four,  awnless;  those  of  the  staminate  spikelet  acute; 
those  of  the  pistillate  very  broad  and  obt.use  or  emarginate. 
Grain  hard,  only  partially  inclosed  by  the  fruiting  glumes. 
A  well-known  tall  and  striking  annual  grass  with  erect  stems 
and  broad  leaves.  The  terminal  staminate  inflorescence  forms 
the  "spindle"  [tassel],  and  the  long  projecting  styles  of  the 
pistillate  flowers  constitute  the  "silk."  The  cob  is  formed  by 
the  union  of  the  axes  of  several  female  spikes  into  a  much 
thickened  body.  Species  one  or  two,  of  American  origin, 
presenting  many  varieties  in  cultivation  known  as  corn,  Indian 
corn  or  maize." 

From  these  descriptions  of  the  two  monotypic  genera,  it  is 
seen  that  Euchlczna  mexicana  Schrad.,  the  common  teosinte, 
is  not  greatly  different  from  Zea  mays  L.,  our  ordinary  maize. 
Indeed  to  one  who  has  grown  and  followed  the  extraordinary 
variability  of  both,  it  does  not  seem  a  greater  step  from  teosinte 
to  the  maize  most  similar  to  it  —  the  short  many  branched 
pop  or  flint  types  —  than  it  does  from  the  small  dwarf  pop 
maize  to  the  giant  dent  forms.  Teosinte  is  perfectly  fertile 
with  maize,  which  fact  has  led  to  some  confusion,  for  Watson 
('91)  thinking  that  hybrids  between  the  two  constituted  a  pure 
wild  species,  named  it  Zea  canina  Watson.  Segura  (Harsh- 
berger,  '96),  however,  by  remaking  the  crosses  and  growing 
them  near  the  region  where  the  "Zea  canina"  was  found,  clearly 
proved  the  true  nature  of  the  latter.  Harshberger  ('93)  first 
fell  into  the  same  error  as  Watson  but  later  (Harshberger  '96) 


12  INHERITANCE  IN  MAIZE. 

discovering  the  true  state  of  affairs  suggested  that  maize  origi- 
nated either  from  (1)  a  cross  between  teosinte  and  some  extinct 
but  closely  related  plant,  which  by  variation  under  a  better 
environment  finally  produced  a  plant  with  larger  maize-like 
ears;  or  that  it  came  from  (2)  a  cross  between  teosinte  and  a 
race  of  the  latter  that  had  varied  under  long  continued  culti- 
vation. The  basis  of  Harshberger's  argument  that  teo  inte 
must  have  been  crossed  by  another  form  is  his  idea  that  only 
in  the  progeny  from  a  cross  would  sufficient  variability  have 
appeared  to  have  produced  the  more  vigorous  plant  —  the 
aboriginal  maize. 

More  recently  Montgomery  [  :  06]  has  advanced  the  theory 
that  teosinte  and  maize  are  both  descended  from  an  unknown 
many-branched  grass  whose  branches  terminated  in  a  panicle 
of  spikelets  bearing  hermaphrodite  flowers.  He  says:  "As 
evolution  progressed,  the  central  tassel  came  to  produce  only 
staminate  flowers,  these  being  higher  and  in  a  better  position 
to  fertilize  the  flowers  on  the  lower  branches.  At  the  same 
time,  the  lateral  branches  came  to  produce  only  pistillate 
flowers,  their  position  not  being  favorable  as  pollen  producers, 
while,  on  the  contrary,  they  were  favorably  placed  to  receive 
pollen.  This  difl^erentiation  in  the  flowers  was  accompanied 
by  a  shortening  of  the  internodes  of  the  lateral  branches  until 
they  were  entirely  enclosed  in  the  leaf  sheaths  [the  husks]." 
The  especial  difference  between  the  evolution  of  teosinte  and 
of  maize  was  thought  to  have  been  in  the  development  of  the 
ear  of  the  first  from  the  lateral  branches  of  the  tassel-like  panicle 
and  the  ear  of  the  second  from  its  central  spike.  This  argument 
of  Montgomery  is  directly  opposed  to  the  old  theory  that  the 
cob  of  modern  maize  is  the  result  of  a  fusion  of  a  number  of 
two-rowed  pistillate  spikelets  such  as  are  found  upon  teosinte. 
His  theory  then,  emphasizes  the  nature  of  the  changes  that 
took  place;  Harshberger's  theory,  the  way  they  were  trans- 
mitted. > 

In  addition  to  these  views  it  seems  only  necessary  to  mention 
that  since  maize  is  the  only  grass  with  a  naked  seed,  the  podded 
variety  Z.  mays  tunicata  Sturt.  is  by  many  considered  to  be  an 
earlier  stage  in  maize  development. 

Our  own  views  on  the  subject  have  resulted  from  a  considera- 
tion of  the  behavior  of  the  characters  of  the  various  races  of 


PLATE    I. 


a.     Ear  with  hermaphrodite  flowers  from  the  dwarf  plant  which  appeared 
in   Stoweh's   Everg-reen   suRar  maize. 


b.     Mature   seeds  on   male   spike   of  plant    heterozygous    for    starchiness, 
showing   segregation.     A    common   physiological    fluctuation. 


Abnormalities 


ORIGIN  OF  THE  PLANT.  13 

maize  when  crossed,  the  data  on  which  they  are  based  being^ 
given  later.  The  matter  is  largely  speculation  and  should  be 
considered  as  such.  It  is  merely  the  simplest  manner  of  inter- 
preting the  known  facts,  by  connecting  maize  with  the  othe-i 
Maydese  by  a  short  series  of  changes  that  involve  characters 
that  mendelize.  On  the  whole  it  does  not  differ  greatly  from 
Montgomery's  theory. 

Since  we  now  believe  that  the  essential  role  of  hybridization 
is  to  recombine  the  characters  possessed  by  the  parent  plants 
in  definite  ratios  without  actually  producing  anything  new, 
[new  combinations  may  produce  characters  formerly  unknown], 
there  is  no  necessity  of  postulating  hybridization  of  teosinte 
with  a  more  maize-like  variety.  It  is  known  that  when  teosinte 
is  cultivated  in  rich  soil  it  sometimes  produces  ears  having 
an  irregular  development  of  four  rows.  This  is  only  an 
expression  of  one  of  the  commonest  modes  of  variation,  repeti- 
tion of  parts  or  meristic  variation.  This  variation  in  the  ear 
has  taken  place  again  and  again  in  maize  and  is  inherited 
although  sometimes  obscured  by  physiological  fluctuation. 
The  ear  of  maize  then  is  a  meristic  variation  produced  from  the 
central  spike  of  the  tassel  of  the  lateral  branches  of  teosinte 
or  of  a  teosinte-like  plant,  and  not  a  fusion  of  the  lateral  spike- 
lets.  Lateral  spikelets  still  appear  in  maize,  apparently  as  if 
variation  ran  in  grooves  or  paths  of  least  resistance.  This 
character  has  been  found  to  segregate  in  a  manner  essentially 
Mendelian.  The  podded  character  also  mendelizes  and  is 
allelomorphic  to  its  absence.  If  then  progressive  meristic 
variations  occurred  in  the  central  spikes  of  the  side  branches 
of  the  teosinte-like  ancestor,  followed  by  retrogressive  varia- 
tions affecting  both  the  lateral  spikes  of  the  lateral  branches 
and  the  pod  character,  a  plant  would  have  originated  bearing 
naked  hermophroditic  ears.  Further  change  might  easily 
have  come  about,  as  Montgomery  suggests,  by  a  shortening 
of  the  side  branches  producing  the  modern  husk,  and  finally 
the  origination  of  the  monoecious  character.  The  latter  occur- 
rence is  not  at  all  hard  to  picture  for  the  change  of  the  staminate 
inflorescence  to  an  hermaphroditic  or  even  a  pistillate  one,  is 
something  which  is  exceedingly  common  in  all  or  almost  all 
strains  of  maize.  It  is  a  physiological  fluctuation  produced 
by  excessive  rainfall  and  fertile  soil.    The  appearance  of  stamens 


14  INHERITANCE  IN  MAIZE. 

on  the  modern  maize  ear  is  much  more  rare  but  that  it  does 
occur  is  shown  by  the  ear  pictured  in  Plate  I.  In  fact  one  of 
our  sterile  dwarf  mutations  had  nothing  but  hermaphroditic 
flowers. 

The    Varieties  of  Maize. 

Although  all  of  the  varied  forms  of  maize  are  regarded  by 
modern  taxonomists  as  sub-divisions  of  the  species  Zea  mays 
L.,  many  varieties  have  at  various  times  been  given  specific 
rank.  The  Index  Kewensis  gives  the  six  following  types  as 
species.  The  original  sources  have  been  consulted  but  the 
descriptions  have  been  shortened  to  include  only  essential  facts. 

Z.  Curagua,  Molina,  J.  I.  Saggio  sulla  storia  naturale  del 
Chili,  pp.  306,  Bologna,  1810.  =  Z.  mays. 

This  variety  is  distinguished  by  its  serrate  leaf-edge.  It 
has  never  been  cultivated  in  the  United  States,  but  appears 
to  be  a  flint  type,  Z.  mays  indurata.  Syn.  Z.  Caragua,  Stend. 
Nom.  ed  II,  ii.  797. 

Z.  erythrolepsis,  Bonafous,  M.  Histoire  naturelle,  agricole 
et  economique  du  Mais.  Folio,  pp.  181,  Plates  19,  Paris,  1836, 
=  Z.  m,ays. 

"Glumis  rubris,  seminibus  compressis."  "Le  Mais  a  rafle 
rouge  cultive  sur  les  rives  du  Missouri,  se  distinque  par  I'aplatis- 
sement  de  ses  grains,  et  surtout  par  le  coleur  rouge  des  ecailles 
et  corallines  de  I'epi  femelle.  La  Constance  de  ce  caractere 
tend  a  lui  meriter  le  titre  d'espece." 

This  form  could  hardly  be  considered  a  variety  as  it  is  a 
common  variation  in  all  of  the  commonly  recognized  varieties. 

Z.  hirta,  Bonafous,  M.  Note  surune  nouvelle  espece  de  Mais. 
Ann,  Sci.  Nat.  Ser.  I  v.  17;  156-158.  1829.  =  Z.  mays.  '' Foliis 
hirtis  et  dependentibus;  spiculis  m,asculis  sessilibus,  diandris 
triandrisve;  antheris  subaureis.'' 

A  good  variety,  originally  sent  to  Bonafous  from  Balbis  of 
the  Jardin  des  Plantes  de  Lyon.  It  varies  into  a  series  of  flint, 
pop  and  dent  types. 

Z.  japonica,  Van  Houtte,  Fl.  des  Serres,  XVI  (1865-67),  121. 
t.  1673-74.  1867.  =Z.  mays.  Syn.  Z.  vittata,  Hort.  and  Z. 
variegata,  Hort. 

A  small  variety  with  leaves  variously  striped  with  white. 
A  small  flint  type  is  the  one  chiefly  cultivated  for  ornament, 


VARIETIES  OF  MAIZE.  15 

but  the  variety  occurs  again  and  again  in  fields  of  all  of  our 
common  maize  strains.  It  could  undoubtedly  be  isolated  pure 
by  careful  selection  of  these  individuals. 

Zea  macrosperma  Klotzsch.  Bot.  Zeitung  9;  718.  1851. 
In  der  Sitzung  des  Ges.  naturf.  Freunde  zu  Berlin.  =Z.  mays. 
Seed  received  by  Humboldt  from  Cuzco.  It  is  simply  a  large 
seeded  dented  starchy  type. 

Zea  rostrata,  Bonafous,  M.  Ann.  Soc.  Agr.  Lyon.  v.  (1842), 
197.  =Z.  mays.  Simply  a  hook-seeded  form  of  pop  maize, 
somewhat  similar  to  our  common  rice  pop. 

Of  these  types  Z.  mays  Curagua  Molina  and  Z.  mays  hirta 
Bonafous  might  be  considered  as  good  varieties.  The  four 
remaining  names  and  also  the  varieties  of  Z.  mays  listed  in  the 
Index  Kewensis  might  well  be  placed  under  the  classification 
porposed  by  Sturtevant  ('99),  leaving  out  his  Zea  mays  amy- 
leasaccharata  because  the  latter  is  a  type  which  is  probably 
identical  with  the  "flinty"  sweet  corns  with  which  canners 
have  so  much  trouble.  The  three  ears  from  the  San  Padro 
Indian  collection  sent  to  Sturtevant  by  Palmer,  and  upon 
which  he  based  the  variety,  failed  to  yield  a  mature  crop  in 
Geneva,  New  York.  It  is  therefore  unknown  whether  this 
type  would  really  prove  true.  Sturtevant's  classification 
follows  although  I  have  added  the  word  mays  and  have  listed 
them  as  varieties  instead  of  species.  It  is  not  strictly  correct 
to  give  him  as  the  authority  for  the  names,  as  he  used  them 
specifically,  but  since  they  have  come  into  general  use  in  the 
United  States  it  seems  more  convenient  to  keep  them.  Sturte- 
vant himself  based  his  claim  for  separate  species  principally 
upon  the  fact  that  intermediates  were  either  absent  or  rare. 
This  fact  comes  about,  as  will  be  shown  later,  from  the  alter- 
native manner  in  which  the  distinguishing  characters  are 
inherited.  In  reality  many  other  characters  are  inherited  in 
the  same  manner,  and  it  is  only  because  the  chief  characters 
of  these  five  varieties  are  striking  to  the  eye  that  it  is  advanta- 
geous to  keep  them  in  use. 

Zea  mays  tunicata,  the  pod  corns.  Sturtevant,  Bui.  Torr. 
Bot.  Club  1894,  p.  355  (Also  St.  Hil.,  Ann.  Sci.  Nat.  16;  p. 
143,  fide  De  Candolle).  A  form  in  which  each  kernel  is  enclosed 
in  husks  (usually  four)  besides  the  foliaceous  bracts  that  enclose 
the  ear. 


i6  INHERITANCE  IN  MAIZE. 

This  form  was  first  described  by  C.  Bauhin  in  1623,  and  has 
been  the  basis  of  a  long  list  of  synonyms  since  that  time.  It 
is  probable  that  the  prototype  of  the  species  possessed  this 
character  for  it  would  thus  be  linked  closer  to  the  other  May- 
dese.  The  strains  now  obtainable  under  this  name  have  been 
hybridized  until  ears  can  be  found  whose  kernels  run  the  whole 
gamut  of  the  other  four  kinds.  The  tendency  of  plants  to 
form  anew  characters  once  possessed  that  have  been  lost,  is 
well  illustrated  here.  We  have  come  across  several  ears  of  our 
ordinary  varieties  in  which  a  few  of  the  kernels  at  the  base 
have  been  podded.  Sturtevant  gives  two  authentic  cases 
where  fully  podded  ears  have  appeared  in  other  varieties  under 
such  conditions  that  it  is  very  improbable  that  it  was  the  result 
of  hybridization. 

Zea  mays  everta,  the  pop  corns.  Sturtevant,  Bui.  Torr.  Bot. 
Club,  1894,  p.  324. 

"This  [species]  group  is  characterized  by  the  excessive  pro- 
portion of  the  corneous  [starch  in  the]  endosperm  and  the  small 
size  of  the  kernels  and  ear.  The  best  varieties  have  a  corneous 
endosperm  throughout.  This  gives  the  property  of  popping, 
which  is  the  complete  eversion  or  turning  inside  out  of  the 
kernel  through  the  explosion  of  the  contained  moisture  on  the 
application  of  heat." 

Strains  of  the  pop  maizes  are  the  smallest  of  our  cultivated 
corns,  and  although  there  are  varieties  that  reach  a  height  of 
nine  feet  when  cultivated  on  fertile  soil,  plants  comparable  in 
size  to  the  average  dent  or  starchy  maize  are  never  found. 
There  appears  to  be  a  distinct  correlation  between  size  of  seed 
and  size  of  plant;  therefore,  since  one  never  obtains  large  size 
seeds  without  a  development  of  soft  starchy  matter,  pop  ker- 
nels much  larger  than  those  now  grown  are  not  likely  to  be 
produced  through  selection  or  hybridization. 

Two  forms  of  seed  are  known  in  the  pop  corns;  one  is  simply 
a  small  seed  with  rounded  crown  similar  in  shape  to  the  small 
flints;  the  other,  characteristic  only  of  pop  corns,  is  peaked 
at  the  point  where  the  style  or  "silk"  was  attached. 

Other  variations  such  as  purple  colored  aleurone  cells,  yellow 
endosperm,  red  silks,  and  red  and  variegated  pericarps  charac- 
terize the  pop  maizes  in  common  with  the  flint,  sweet,  dent 
and  starchy  corns.     The  modal  number  of  rows  also  varies 


VARIETIES  OF  MAIZE.  17 

in  different  varieties  from  eight  to  sixteen.  In  this,  pop  maize 
is  similar  to  dent,  sweet  and  starchy,  but  different  from  flint 
maize.  It  is  doubtful  whether  any  true  flint  maize  exists  with 
a  mode  for  number  of  rows  higher  than  twelve. 

Zea  mays  indurata,  the  flint  corns.  Sturtevant,  Bui.  Torr. 
Bot.  Club,  1894,  p.  327. 

This  group  is  characterized  by  the  seeds  having  a  corneous 
starchy  endosperm,  surrounding  a  soft  starchy  center  immedi- 
ately behind  or  partially  surrounding  the  embryo.  The  strains 
in  common  cultivation  are  considerably  larger  than  the  pop 
corns,  but  varieties  do  exist  which  form  a  definite  series  from 
pop  to  dent  differing  only  by  the  amount  and  extent  to  which 
soft  starch  replaces  corneous  starch  in  the  endosperm.  The 
same  color  varieties  that  were  described  for  pop  corns  occur. 

Zea' mays  indentata,  the  dent  corns.  Sturtevant,  Bui.  Torr. 
Bot.  Club,  1894,  p.  329. 

A  group  characterized  by  the  extension  of  the  soft  starch 
until  it  completely  covers  the  summit  of  the  seed.  Corneous 
starch,  however  remains  at  the  sides  of  the  kernel  and  acts  as 
a  frame  work  to  support  the  drying  seed.  The  soft  starchy 
portion  shrinking  in  drying  to  a  much  greater  extent  than  the 
other  forms  a  characteristic  indentation.  Dent  varieties  occur 
averaging  from  five  feet  to  twenty  feet  (reported)  in  height, 
with  from  eight  to  twenty-four  rows  as  the  modes  (extremes 
to  thirty-six  rows) .     The  usual  color  varieties  occur. 

Zea  mays  amylacea,  the  soft  or  flour  corns.  Sturtevant, 
Bui.  Torr.  Bot.  Club,  1894,  p.  331. 

A  group  characterized  by  entire  absence  of  corneous  starch 
in  the  endosperm.  Uniform  shrinkage  in  drying  usually  gives 
a  seed  with  no  indentation.  The  mummy  corns  of  Peru,  Mexico 
and  the  southern  United  States  appear  to  belong  to  this  group, 
but  this  is  not  absolutely  certain.  The  specimens  that  we  have 
examined  belonging  to  the  New  York  Botanical  Garden  might 
have  been  flint  corns  which  owe  their  floury  appearance  to 
partial  decomposition. 

This  group  marks  the  final  disappearance  of  corneous  starch 
in  the  endosperm.  It  is  the  end  of  a  series  beginning  with  the 
pop  corns  and  coming  up  through  the  flints  and  dents.  For 
this  reason  one  might  expect  them  to  possess  the  largest  seeds,  as 
the  length  of  time  necessary  for  maturing  the  seed  undoubtedly 


i8  INHERITANCE  IN  MAIZE. 

has  something  to  do  with  the  amount  of  soft  starch  formed. 
The  plants  are  indeed  large,  but  seeds  occur  varying  from  the 
size  of  the  smaller  flints  to  that  of  the  larger  dents.  The  origin 
of  the  starchy  corns  is  not  due  simply  to  their  correlation  with 
the  general  plant  structure  and  therefore  a  simultaneous  origin 
with  large  varieties,  but  is  dependent  upon  a  separate  character 
or  group  of  characters.     The  usual  color  varieties  occur. 

Zea  mays  saccharata,  the  sweet  corns.  Sturtevant,  Bui. 
Torr.  Bot.  Club,  1894,  p.  333. 

"A  well  defined  group  characterized  by  the  translucent  horny 
appearance  of  the  kernels  and  their  more  or  less  crinkled, 
wrinkled  or  shriveled  condition."  The  sweet  corns  are  simply 
pop,  flint  and  dent  varieties  (East  :  09)  that  have  lost  their 
ability  to  mature  starch  normally.  Some  few  starch  grains 
are  produced  but  they  are  generally  small,  angular  and  abortive. 
The  reserve  material  of  the  endosperm  seems  to  undergo  a 
decomposition  to  cane  sugar  and  the  various  hexoses.  There 
is  apparently  something  more  than  a  simple  non-development 
of  starch,  for  the  sweet  corns  in  the  "milk"  state  contain  greater 
percentages  of  sugar  than  do  the  starchy  varieties  in  a  similar 
stage  of  ripeness.     The  same  color  varieties  occur. 

The  Prohlein  and  its    Treatment. 

It  is  apparent  that  maize  furnishes  an  admirable  series  of 
types  which  are  perfectly  fertile  among  themselves.  The 
primary  object  of  our  work  is  to  obtain  pure  forms  of  these 
diverse  types  by  inbreeding,  then  to  test  the  mechanism  of 
inheritance  of  each  separate  character  by  controlled  matings 
and  an  analysis  of  the  resulting  progeny.  In  doing  this  we 
simply  follow  Mendel's  method  of  the  individual  analysis  of 
pedigree  cultures. 

The  specific  questions  attacked  are  numerous.  Our  principal 
object  is  to  find  whether  the  different  characters  under  obser- 
vation all  obey  the  same  law  of  heredity  or  whether  separate 
principles  are  involved,  and  whether  characters  apparently 
inherited  independently  are  not  sometimes  correlated  with  each 
other.  The  question  of  dominance  of  a  character  in  the  first 
generation  of  a  cross  has  also  interested  us.  Some  characters 
are  perfectly  dominant,  other  characters  imperfectly  dominant, 
while  still  others  form  heterozygous  combinations  differing  from 


THE  PROBLEM.  19 

either  of  the  parents.  There  are  even  cases  in  which  dominance 
appears  to  be  reversible.  If  such  a  thing  is  possible,  an  explana- 
tion is  desirable.  The  study  of  the  phenomenon  of  Xenia, 
which  has  already  formed  the  basal  object  of  Correns'  (  :  01) 
fine  monograph,  throws  gome  light  on  these  questions. 

Another  object  we  have  kept  in  mind  is  the  problem  of  the 
purity  of  extracted  homozygotes.  It  is  a  matter  of  common 
knowledge  that  characters  that  have  been  lost  through  retro- 
gressive variations  —  characters  that  behave  as  mono-hybrids 
in  inheritance  —  often  reappear.  The  reverse  of  this  pheno- 
menon is  also  true.  Is  it  because  there  is  a  phylogenetic  "path" 
in  which  these  changes  run,  so  that  the  same  variation  appears 
again  and  again,  or  is  there  no  absolute  purity  of  the  germ-cells 
but  only  a  comparative  purity  as  indicated  by  Morgan  (  :  10)  ? 

The  idea  of  prepotency  has  been  held  with  great  tenacity 
up  to  the  present  time.  We  hope  these  researches  will  throw 
some  light  upon  this  subject  of  so  much  importance  to  practical 
breeders.  If  there  are  individuals  whose  constitution  is  such 
that  chance  production  of  zygotes  is  interfered  with,  the  fact 
brings  many  complications  into  the  study  of  inheritance;  but 
such  complications  must  not  interfere  with  the  facts.  Various 
other  questions  will  be  discussed  in  the  proper  places  and  for 
this  reason  will  not  be  considered  further  here. 

It  may  be  well  to  mention  that  although  these  questions 
smack  of  the  technical,  it  is  maintained  that  in  just  so  far  as 
one  contributes  toward  their  solution,  that  far  is  the  broad 
practical  problem  of  better  methods  for  the  production  of  new 
economic  maize  types  solved.  The  questions  of  purity  of 
homozygotes,  inheritance  of  size  and  number  of  ear-rows  in 
the  different  sub-species  are  easily  seen  to  be  of  practical  agri- 
cultural importance.  Other  questions  may  seem  of  less  import- 
ance or  even  of  no  importance  from  this  point  of  view,  but  this 
is  fallacious  as  is  easily  shown  by  illustrations  from  the  science 
of  chemistry  where  abstruse  theoretical  researches  have  con- 
tinually proved  to  be  the  most  practical  in  the  end. 

In  certain  quarters  there  has  been  a  marked  reaction  against 
the  continued  Mendelian  interpretation  which  has  been  given 
to  every  paper  published  since  the  year  nineteen  hundred  in 
which  actual  experimental  studies  concerning  the  mechanism 
of  inheritance  have  been  reported.     This  reaction  has  taken 


20  INHERITANCE  IN  MAIZE. 

the  form  of  a  philosophical  query  as  to  whether  the  characters 
of  the  organic  complex  of  which  living  organisms  are  composed 
can  in  any  sense  be  dissected  and  analyzed  into  the  "miits" 
of  heredity  which  are  the  basis  of  Mendelian  inheritance. 
Further  it  has  been  questioned  whether  there  is  any  justifica- 
tion for  the  increasing  complexity  with  which  Mendelian 
formulse  are  involved.  It  has  been  argued  that  with  a  mul- 
tiplicity of  "factors"  any  particular  case  can  be  interpreted 
as  segregating  according  to  the  Mendelian  hypothesis.  For 
these  reasons  the  writers  wish  to  have  their  position  in  report- 
ing the  following  investigations  distinctly  understood  at  the 
beginning. 

It  is  fully  understood  that  there  is  danger  in  improper  analysis 
of  complex  ratios  from  pedigree  cultures.  This  is  inevitable. 
Yet  it  is  not  a  more  pertinent  criticism  to  condemn  complexity 
in  biological  facts  than  it  is  to  frown  upon  the  intricacies  of 
modern  organic  chemistry  because  it  is  so  different  from  the 
simple  chemistry  of  Liebig.  The  answer  is  that  the  facts  of 
heredity  are  complex. 

In  regard  to  the  question  of  the  ultimate  nature  of  unit 
characters  or  the  possibility  of  absolute  segregation  of  characters 
in  the  germ-cells  so  that  in  the  recessive  there  is  actual  absence 
of  the  character  (gene)  in  question,  we  must  await  more  results 
from  the  different  points  of  view  of  the  breeder,  the  cytologist, 
the  physiologist  and  the  physiological  chemist.  The  facts 
reported  in  genetic  investigations  remain  indelible.  The 
interpretation  of  these  facts  may  or  may  not  be  correct;  they 
simply  arbitrarily  represent  the  facts  in  a  convenient  system 
of  notation  much  as  the  facts  of  chemistry  are  represented  by 
structural  formulae.  This  is  the  idea  in  the  minds  of  the 
authors  in  the  following  report.  It  is  thought  moreover  to 
represent  the  attitude  of  most  genetic  investigators  and  the 
excuse  for  making  the  above  statements  lies  in  the  fact  that 
unfortunately  one  often  finds  no  appreciation  of  this  attitude 
by  biologists  not  actually  engaged  in  genetic  research. 

We  have,  then,  used  the  ordinary  Mendelian  notation,  with 
allelomorphic  pairs  interpreted  as  presence  and  absence  of 
characters  not  because  we  know  that  there  is  actual  absence 
but  because  this  interpretation  fits  our  present  knowledge. 
We  have  interpreted  complex  characters  such  as  height  which 


PREVIOUS   INVESTIGATIONS.  21 

we  are  not  able  to  analyze  completely,  as  segregating  characters. 
The  conclusion  that  there  is  a  segregation  in  the  second  hybrid 
generation  very  much  in  excess  of  the  sum  of  the  non-inherited 
fluctuation  and  of  other  variation  due  to  the  heterozygous  con- 
dition of  the  pure  (?)  forms  used  and  also  of  their  combination 
in  the  first  hybrid  generation,  is  justified  by  the  data.  This  is 
the  essence  of  Mendelian  theory;  and,  whether  absolutely 
correct  or  not,  it  is  an  interpretation  that  cannot  fail  to  be 
valuable  to  the  commercial  plant  breeder.  It  gives  him  some 
knowledge  of  what  may  be  expected  in  his  endeavors  to  produce 
new  types  of  maize  by  hybridization. 

It  might  also  be  mentioned  that  following  Johannsen,  the 
word  "gene"  has  been  used  to  signify  that  substance  present 
in  the  germ-cell  which  represents  potentially  the  "unit  char- 
acter" or  whatever  it  may  be  called  that  acts  as  an  entity  in 
heredity. 

Previous  Work  on  Inheritance  in  Maize. 

Before  describing  in  detail  the  material  used  in  these  experi- 
ments it  may  be  well  to  give  a  short  summation  of  the  previous 
work  in  the  field. 

The  early  hybridists,  Camerarius,  Logan,  Pontedera  and 
Henschel,  each  made  a  desultory  study  of  maize  crosses,  but 
obtained  no  results  of  present  interest.  Hardly  more  satis- 
factory are  the  papers  of  Dudley  (1724),  Sageret  ('26),  Puvis 
('37),  Gartner  ('49),  Naudin  ('63),  Hildebrand  ('67,  '68), 
Vilmorin  ('67)  and  Focke  ('81),  although  these  researches  — 
representing  work  of  the  principal  students  of  hybridization 
of  the  period  —  each  gives  several  observations  concerning  the 
immediate  effect  of  pollen  upon  the  endosperm,  —  that 
phenomenon  called  Xenia  by  Focke  ('81).  These  observations, 
however,  can  hardly  be  compared  with  those  made  since  the 
cause  of  Xenia  was  discovered  for  the  obvious  reason  that  the 
facts  concerning  the  changes  in  the  endosperm  were  almost 
lost  to  sight  in  the  search  for  effect  of  cross-pollination  on  the 
tissues  of  the  maternal  parent. 

In  the  work  of  a  slightly  later  period  particularly  in  the 
United  States  (Kellerman  and  Swingle  '89,  '90;  McCluer  '92; 
Morrow  and  Gardner  '92)  a  great  improvement  was  made  in 


22  INHERITANCE  IN  MAIZE. 

the  methods  of  investigation  employed.  The  parental  stock 
was  often  inbred  to  establish  its  purity,  crosses  were  made  by 
hand  upon  protected  flowers,  and  the  resulting  progeny  were 
studied  with  great  care.  Many  facts  of  inheritance  are  uncon- 
sciously reported  in  their  papers  which  are  confirmed  in  the 
post-Mendelian  work  which  gives  them  a  meaning  For  exam- 
ple one  finds  these  data  in  Kellerman  and  Swingle  ('91).  A 
*chance  hybrid  evidently  produced  by  the  pollination  of  a  white 
maize  with  pollen  from  a  variety  with  purple  aleurone  cells  was 
inbred.  A  hand-pollinated  ear  contained  370  seeds,  of  which 
206  were  blue,  71  pink,  71  orange-yellow  and  22  pure  white. 
One  wonders  how  the  essential  facts  of  dominance  and  segre- 
gation remained  unnoticed  in  the  face  of  such  ratios  as  this. 
But  even  if  it  is  interesting  to  reread  these  papers  and  consider 
them  from  a  more  modern  viewpoint,  it  is  hardly  profitable 
to  discuss  them  further  here.  The  work  previous  to  1900  was 
in  the  wrong  epoch,  and  since  that  time  three  valuable  con- 
tributions to  the  subject  in  hand  have  been  made.  (De  Vries 
1899  and  1900,  Correns  1,899,  1900  and  1901,  and  Lock  1906.) 

It  is  interesting  at  least,  to  note  that  in  the  cases  of  both 
De  Vries  and  of  Correns  the  studies  of  maize  hybrids  in  which 
presence  and  absence  of  yellow  and  .presence  and  absence  of 
starch  in  the  endosperm  were  concerned,  contributed  largely 
to  their  independent  discoveries  of  dominance  and  segrega- 
tion in  hybrids,  which  they  both  unselfishly  credited  entirely 
to  Mendel  after  their  discovery  of  his  previous  paper.  Thus 
Zea  mays  shares  with  Pisum  sativum  the  honor  of  being  the 
subject  material  in  the  establishment  of  Mendel's  laws. 

Correns'  (:01)  beautiful  monograph  was  written  with  the 
especial  idea  of  furnishing  an  explanation  of  the  phenomenon  of 
Xenia,  but  it  naturally  contributed  a  large  amount  of  data 
upon  the  mechanism  of  inheritance  of  the  characters  with  which 
he  worked. 

Correns'  technique  was  as  follows.  The  seeds  were  planted 
first  in  pots,  allowed  to  attain  a  healthy  start,  and  finally  trans- 
planted to  the  field.  In  the  first  year  (1894)  the  plants  to  be 
used  as  "mothers"  were  planted  together  in  his  experiment 
field,  castrated  at  the  right  time  and  the  silks  protected  between 

*  The  immediate  parents  were  thought  to  have  been  white,  but 
this  was  probably  an  error. 


PREVIOUS   INVESTIGATIONS.  23 

pollinations  with  paper  bags.  The  individuals  that  furnished 
the  pollen  were  planted  together  in  places  apart  from  the  pro- 
posed mother  plants  and  from  them  pieces  of  the  male  panicles 
(tassels)  were  carried  in  glass  bottles  to  the  mother  plants. 
Slight  changes  in  the  plan  of  planting  were  made  in  1895  and 
1896,  but  I  cannot  find  in  any  case  that  either  the  male  flowers 
were  protected  from  foreign  pollen  during  their  maturation 
or  that  special  care  was  taken  to  have  pollen  for  a  cross  fur- 
nished by  an  individual  plant.  Furthermore  in  handling  the 
hybrids  individuals  were  not  selfed  but  bred  inter  se.  Some 
of  the  families  were  given  to  gardeners  who  were  growing  no  other 
maize,  while  others  were  detasseled  and  naturally  pollinated 
en  masse  with  the  pollen  of  a  pure  race.  The  first  method 
predominated.  We  can  see  then  that  the  methods  in  use 
furnished  correct  results  only  when  the  characters  in  question 
were  simple  and  of  such  nature  that  the  races  could  be  kept 
pure  by  inspection.  Complex  ratios  such  as  are  furnished 
when  maize  with  purple  aleurone  cells  is  crossed  with  various 
white  maizes  differing  in  gametic  structure,  could  not  possibly 
be  analyzed  correctly. 

Correns  reached  conclusions  regarding  the  mode  of  inheri- 
tance of  the  following  characters  but  it  must  be  borne  in  mind 
that  these  results  came  from  the  study  of  data  more  or  less 
massed,  and  not  the  study  of  individual  crosses  in  as  precise 
a  manner  as  that  outlined  by  Mendel. 

Yellow  endosperm  was  found  to  be  dominant  to  its  absence, 
and  starchiness  dominant  to  absence  of  starchiness  (sweet).  Both 
of  these  characters  behaved  as  Mendelian  mono-hybrids.  It 
cannot  be  definitely  stated,  however,  that  crosses  between  all 
races  of  maize  where  presence  and  absence  of  these  characters 
are  concerned  would  give  the  same  results.  Long  aleurone 
cells  also  proved  dominant  to  short  aleurone  cells,  and  red 
pericarp  to  absence  of  red,  but  Correns  was  not  entirely  satis- 
fied that  these  characters  behaved  as  simple  Mendelian  mono- 
hybrids  although  he  supposed  this  to  be  the  case. 

Purple  aleurone  cells  appeared  to  form  an  allellomorphic 
pair  with  absence  of  purple,  but  he  found  that  the  heterozy- 
gotes  when  bred  inter  se  did  not  give  the  normal  number  of 
whites.  What  he  took  to  be  heterozygotes  of  the  same  char- 
acter were  either  pure  purple,   partial  purple,   or  pure  white 


24  INHERITANCE  IN  MAIZE. 

when  the  purple  was  used  as  the  male  parent.  In  the  reverse 
cross  the  purple  appeared  to  be  fully  dominant.  Correns 
(:01)  endeavors  to  explain  this  phenomenon  by  the  fact  that 
in  the  formation  of  the  hybrid  endosperm  two  nuclei  come 
from  the  female  and  but  one  from  the  male  parent.  He  sup- 
poses that  in  some  cases  this  may  cause  a  dominance  of  the 
female  characters.  This  purple  character  seemed  to  interfere 
with  normal  inheritance  in  still  another  case  (Correns  :02), 
where  a  blue  sweet  corn  was  crossed  with  a  non  blue  pop.  Here 
the  second  generation  yielded  only  about  153^%  of  sweet 
kernels  out  of  a  total  of  over  8,000.  Pollinated  with  the  reces- 
sive parent  there  appeared  nearly  50%  of  sweet  kernels  so  that 
the  female  germ-cells  seemed  to  have  segregated  normally. 
Correns  suggested  that  in  this  case  the  four  possible  combinations 
of  characters  in  the  germ-cells  did  not  take  place  with  equal 
facility. 

Our  own  data  shows  the  error  in  the  first  case  to  be  due  to 
the  fact  that  white  races  differ  in  their  gametic  structure  in 
characters  which  affect  the  purple  color.  The  observations 
in  the  second  case  have  not  been  confirmed,  but  were  probably 
due  to  improper  classification  of  the  heterozygous  dominants 
and  the  recessives.     (See  starchy  and  non-starchy  crosses.) 

The  shape  and  size  of  seed  and  relative  weight  of  embryo 
and  endosperm  Correns  thought  behaved  in  a  non-Mendelian 
manner,  although  he  was  not  prepared  to  say  in  exactly  what 
manner  these  characters  were  inherited. 

Lock  (  :  06)  carried  out  a  much  more  extended  series  of 
maize  crosses  at  Peradeniya,  Ceylon,  from  1902  to  1906.  His 
technique  in  certain  cases  was  a  considerable  improvement 
on  that  of  Correns  in  that  both  the  male  and  female  infior- 
escences  were  enclosed  in  bags  and  thus  crosses  were  made 
between  single  individuals.  Unfortunately  his  method  was 
later  changed  and  cross  pollination  was  accomplished  by  plant- 
ing the  two  races  in  alternate  rows  on  an  isolated  plot  of  ground, 
and  detasseling  all  plants  of  the  race  which  it  was  proposed  to 
use  as  the  female  parent.  This  method  of  course  gave  no 
chance  to  make  a  proper  analysis  of  complex  characters  for 
could  not  be  known  just  what  gametic  composition  was  pos- 
sessed by  the  male  parent.  This  criticism  was  anticipated 
by  Lock  himself  but  the  method  was  used  because  he  desired 


THE  MATERIAL.  25 

to  have  a  large  amount  of  data  from  which  to  establish  the 
mathematical  accuracy  of  Mendel's  hypothesis  of  definite 
segregation  and  chance  mating.  In  the  cases  of  starchy  and 
non-starchy,  and  yellow  and  non-yellow  endosperm  Lock's 
results  were  in  accord  with  those  of  Correns.  Furthermore 
he  showed  definitely  that  red  pericarp  behaved  as  a  Mendelian 
character,  allelomorphic  to  absence  of  red.  Lock  also  crossed 
indented  and  non-indented  races  and  remarks  that  in  the  F2 
generation  a  high  degree  of  variability  appeared,  but  without 
making  crosses  between  individual  plants  and  studying  the 
progeny  he  could  not  decide  whether  or  not  Mendel's  Law  was 
followed.  No  data  is  reported  on  inheritance  of  height  of 
plants  but  a  number  of  crosses  were  made  between  Fi  plants 
and  the  shorter  of  the  parental  races,  and  he  states  that  no 
segregation  into  short  and  intermediate  plants  took  place.  The 
plants  on  the  contrary  were  remarkably  uniform  in  height  and 
he  believed  blended  inheritance  to  be  the  rule  for  this  character. 

Lock's  results  in  crossing  races  with  purple  aleurone  cells 
with  races  with  non-purple  aleurone  cells  is  so  seriously  com- 
plicated from  the  fact  that  he  followed  out  no  individual  crosses 
that  it  is  impossible  to  criticize  his  data.  From  the  fact  that 
individual  ears  showed  such  different  ratios  as  3  :  1,  9  :  7  and 
1  ;  3  we  may  suspect  that  he  was  dealing  with  white  races  of 
varying  composition  such  as  are  described  in  our  work  on  this 
character. 

These  short  abstracts  from  the  work  of  Correns  and  of  Lock 
do  not  give  an  adequate  idea  of  the  large  amount  of  painstaking 
investigation  for  which  each  should  be  credited  however,  and 
anyone  interested  in  the  subject  should  therefore  consult  the 
original  papers. 

The  Material    Used. 

The  types  of  maize  which  furnished  the  parental  stock  with 
which  crosses  were  made  for  this  series  of  studies  were  in  most 
cases  inbred  by  hand  for  at  least  two  generations  before  any 
hybrids  were  actually  made.  When  this  procedure  was  im- 
possible the  parental  ears  were  obtained  from  various  commer- 
cial growers  who  made  a  specialty  of  the  types  which  they 
furnished.  From  the  maize  obtained  from  them  single  ears 
were  selected  and  planted.     The  plants  forming  the  immediate 


26  INHERITANCE  IN  MAIZE. 

progeny  of  these  ears  were  used  in  part  as  the  parents  of  crosses 
and  in  part  to  inbreed.  When  any  of  the  seeds  from  the  origi- 
nal ear  were  found  to  be  heterozygous  in  any  characters  the 
fact  is  noted  when  the  crosses  are  described.  In  this  manner 
we  were  able  to  determine  the  purity  of  the  parental  stock 
used,  for  all  of  the  grosser  characters.  Of  course  new  varia- 
tions were  continually  isolated  and  these  were  given  numbers 
which  show  their  origin.  For  example,  the  original  stock  of 
Longfellow  corn  is  No.  15;  if,  however,  new  variations  appeared 
in  the  Longfellow  progeny  they  were  numbered  15-1,  15-2,  etc. 
The  following  descriptions,  then,  comprise  only  original 
material;    that  is,  single  ears  of  various  commercial  varieties. 

Zea  mays  tunicafa.     The  podded  corns. 
21.     Podded  maize. 

A  fourteen-rowed  ear  with  four  husks  around  each  kernel  in  addition 
to  ths  usual  paleas.  The  seeds  looked  like  rice  pop;  they  were  small 
but  showed  a  considerable  amount  of  white  starchy  matter. 

Zea  mays  everta.     The  pop  corns. 
20.     A  flint-like  8-row  purple  pop. 

A  pop  with  purple  aleurone  cells,  showing  a  small  amount  of  white 
starchy  matter  immediately  behind  the  embryo,  sufficient  to  keep  the 
seeds  from  popping  well.  Ear  1.5  cm.  long,  11  cm.  in  cir.  Seeds  .9  x  .9 
cm.,  white  endosperm.     Cob  white. 

60.     Tom  Thumb  pop. 

A  dwarf  true  pop.  Ear  7.5  cm.  long,  8  cm.  in  cir.,  12-rowed;  pericarp 
colorless.  Seeds  rounded,  true  pop,  .5  x  .4  cm.,  endosperm  yellow.  Cob 
white. 

23.     White  rice  pop. 

A  white  true  pop.  Ear  15.5  cm.  long,  10  cm.  in  cir.,  16-rowed.  Seeds 
white,  .9  X  .5  cm.,  hooked.     Cob  white. 

26.  A  white,  flint-like  pop. 

A  white  true  pop  with  rounded  flint-like  seeds.  Ear  17  cm.  long, 
9  cm.  in  cir.,  8-rowed.     Seeds  .8  x  .9  cm.  rounded.     Cob  white. 

27.  Red  rice  pop. 

A  true  rice  pop  with  red  pericarp.  Used  only  for  inheritance  of 
pericarp  color. 

28.  White  rice  pop. 

A  true  rice  pop  with  white  or  colorless  pericarp.     Used  only  in  cross 

with  No.  27. 

Zea  mays  indurata.     The  flint  corns. 
4.     Benton  maize. 

An  eight-rowed  race  intermediate  between  the  flint  and  the  dent 
corns.  Ear  34  cm.  long,  14  cm.  in  cir.,  8-rowed,  pericarp  red  becoming 
colorless  at  summit.  Seeds  1.1  x  1.4  cm.,  some  very  slightly  dented; 
endosperm  yellow,  slightly  more  starchy  than  a  true  flint.     Cob  white. 


THE  MATERIAL.  27 

5.     Watson  flint. 

A  true  flint  with  a  pericarp  rose  red  when  developing  in  full  sunlight, 
the  seeds  at  the  tip  usually  showing  simply  red  striations  beginning 
at  point  of  attachment  of  the  silk.  Ear  27  cm.  long,  13  cm.  in  cir.,  8- 
rowed.     Seeds  1.0  x  1.2  cm.,  endosperm  colorless.     Cob  white. 

11.      Sturges'  flint. 

A  twelve-rowed  yellow  flint  race.  Ear  20  cm.  long,  14  cm.  in  cir., 
12-rowed,  pericarp  colorless.  Seeds  1.0x1.0  cm.,  endosperm  yellow. 
Cob  white. 

13.     Sanford  flint. 

An  eight-rowed  race.  Ear  30  cm.  long,  13  cm.  in  cir.,  8-r6wed; 
pericarp  colorless.  Seeds  1.0x1.3  cm.;  endosperm  colorless.  Cob 
white. 

15.     Longfellow  yellow  flint. 

An  eight-rowed  yellow  race.  Ear  27  cm.  long,  11.5  cm.  in  cir.;  8- 
rowed;  pericarp  colorless.  Seeds  .9x1.2  cm.;  endosperm  bright 
yellow.     Cob  white. 

17.     Palmer's  red-nosed  yellow  flint. 

An  eight-rowed  yellow  race.  Ear  22  cm.  long,  12  cm.  in  cir.;  8-rowed; 
pericarp  a  dirty  red  at  the  sides  of  seed  becoming  almost  colorless  at 
summit.  Color  not  deep  as  in  common  red  maize.  Seeds  1.0x1.4 
cm.;    endosperm  yellow.     Cob  white. 

24.  Rhode  Island  white  cap. 

An  eight-rowed  flint  race.  Ear  29  cm.  long,  12  cm.  in  cir.;  8-rowed; 
pericarp  colorless  except  for  a  slight  pink  tinge  of  rose  similar  to  No.  5 
but  less  in  amount.  Seeds  .9x1.2  cm.;  endosperm  colorless.  Cob 
white. 

25.  Brindle  flint. 

A  common  flint  race  not  breeding  true  to  the  character  from  which 
it  derives  its  name,  —  a  mosaic  pericarp  formed  by  slashes  of  dark  red 
extending  irregularly  from  the  point  of  the  attachment  of  the  silk.  Eight- 
rowed  true  flint. 

Zea  mays  indentata.     The  dent  corns. 

2.  Illinois  low  protein  dent. 

A  white  dent  selected  for  low  proteid  content  at  the  Illinois  Agri- 
cultural Experiment  Station  for  eight  generations.  Protein  content 
8.30  per  cent.  Ear  19  cm.  long,  18  cm.  in  cir.;  16-rowed;  pericarp 
colorless.  Seeds  1.5  x  .8  cm.;  endosperm  colorless;  white  starchy 
matter  largely  increased  in  summit  over  usual  dent  type.     Cob  white. 

8.     Illinois  high  protein  dent. 

A  white  dent  selected  for  high  proteid  content  at  the  Illinois  Agri- 
cultural Experiment  Station  for  eight  generations.  Proteid  content 
15.46  per  cent.  Ear  20  cm.  long,  14  cm.  in  cir.;  14-rowed;  pericarp 
colorless.  Seed  1.1  x  .9  cm.;  endosperm  colorless;  white  starchy  matter 
decreased  from  amount  usual  in  dent  types  but  summit  still  well  dented. 
Cob  white. 

3.  Leaming  dent. 

A  yellow  dent  race.  Ear  21  cm.  long,  16  cm.  in  cir.;  20-rowed; 
pericarp  colorless  but  sometimes  very  slightly  tinted  with  dirty  brick 
red  at  sides  of  seeds.  Seeds  1.3  x  .7  cm.;  endosperm  dark  yellow;, 
considerable  soft  starch  at  summit;    well  dented.     Cob  dark  red. 


28  INHERITANCE  IN  MAIZE. 

6.  Learning  dent. 

Same  race  as  No.  3  but  of  different  ancestry.  Ear,  19.5  cm.  long, 
18.5  cm.  in  cir. ;    18-rowed. 

7.  Learning  dent. 

Same  race  as  No.  3  but  of  different  ancestry.  Ear  18  cm.  long,  17 
cm.  in  cir.;    20-rowed. 

9.  Learning  dent. 

Same  race  as  No.  3  but  of  different  ancestry.  Ear  18.5  cm.  long, 
16.5  cm.  in  cir.;    16-rowed. 

12.     Leaming  dent. 

Same  race  as  No.  3  but  of  different  ancestry.  Ear  19  cm.  long,  17 
cm.  in  cir.;    18-rowed. 

16.      Leaming  dent. 

Same  race  as  No.  3  but  of  different  ancestry.  This  ear  was  18-rowed 
and  perfectly  formed.  It  was  surrounded  by  five  lateral  branches  each 
having  either  four  or  eight  rows  of  seeds. 

1.     Missouri  cob  pipe  dent. 

A  very  large  dent  race  characterized  by  large  cob.  Ear  28  cm.  long' 
22.5  cm.  in  cir. ;  cob  14  cm.  in  cir. ;  20-rowed;  pericarp  colorless.  Seeds 
1.5  X  .9  cm.;    endosperm  white.     Red  cob. 

22.     Mosaic  red  dent. 

A  dent  characterized  by  dark  intense  red  pericarp.  Used  only  for 
study  of  that  character. 

Zea  mays  amylacea.     The  flour  corns. 

10.  White  floury. 

A  thoroughly  floury  race,  showing  absolutely  no  corneous  starch. 
Ear  22  cm.  long,  14.5  in  cir.;  14-rowed;  pericarp  colorless.  Seeds  1.2  x 
1.0  cm.;    endosperm  colorless.     Cob  white. 

Zea  mays  saccharata.     The  sweet  corns. 
19.     Stowell's  evergreen. 

A  large-eared  extremely  wrinkled-seeded  late  sugar  corn.  Ear  16 
cm.  long,  15.5  cm.  in  cir.;  14-rowed;  pericarp  colorless.  Seeds  1.4  x  .7 
cm. ;    endosperm  colorless.     Cob  white. 

18.     Early  Crosby. 

A  twelve-rowed  sugar  corn.  Ear  14.5  cm.  long,  14  cm.  in  cir.;  12- 
rowed;  pericarp  colorless.  Seeds  .9  x  .9  cm.;  decidedly  wrinkled  but 
thick  full  seeds;    endosperm  colorless.     Cob  white. 

54.     Black  Mexican. 

An  eight-rowed  sugar  corn  characterized  by  purple  aleurone  cells. 
Ear  13.5  cm.  long,  12  cm.  in  cir.;  8-rowed;  pericarp  colorless.  Seeds 
.9  X  1.1  cm.;    aleurone  cells  purple;    endosperm  colorless. 

Methods    Used. 

In  carrying  out  the  large  amount  of  tedious  routine  work 
necessary  in  the  collection  of  data  from  the  crosses  of  the  above 
types,  a  great  effort  was  made  to  reduce  experimental  errors 


EXPERIMENTAL  METHODS.  29 

to  a  minimuin.  No  part  of  the  work  was  left  to  farm  workmen 
except  the  preparation  of  the  breeding  plots  and  their  culti- 
vation. The  planting,  labeling  of  families,  crossing,  selfing, 
harvesting,  filing  of  seed  and  collection  and  reduction  of  data 
were  done  by  the  authors.  The  senior  author  alone  is  respon- 
sible for  the  details  of  the  work  until  1909.  In  1909  and  1910 
the  senior  and  junior  authors  both  shared  in  the  labor.  Since 
1907  efficient  aid  in  harvesting,  filing  seed,  etc.,  has  been  given 
by  Mr.  C.  D.  Hubbell  of  the  Conn.  Agr.  Exp.  Station.  In 
1910  Mr.  D.  W.  Davis  and  Mr.  0.  E.  White,  graduate  students 
at  Harvard  University,  aided  in  selfing  ears  of  various  selections. 

The  ears  have  always  been  shelled  and  seeds  classified  and 
filed  in  seed  envelopes.  Where  there  has  been  the  least  question 
about  classification  the  work  has  been  duplicated  by  two 
observers.  If  then  there  has  been  a  doubt  concerning  the 
characters  borne  by  particular  seeds,  those  in  question  have 
been  grown  for  another  generation.  The  planting  has  been 
done  from  the  seed  envelopes  directly  to  the  field.  There 
they  were  planted  in  hills  three  and  one-half  feet  apart  each 
way,  four  seeds  to  the  hill.  It  was  not  considered  necessary 
to  start  the  seeds  in  the  greenhouse  in  sterilized  soil  as  is  done 
with  smaller  seeds.  Maize  seed  ver}^  seldom  germinates  after 
remaining  in  the  ground  over  the  winter  in  this  climate.  Fur- 
thermore the  corn  which  was  not  hand  pollinated  was  not 
husked  directly  on  the  field  so  that  there  was  but  little  chance 
that  any  seeds  should  remain  upon  the  ground.  Great  care 
was  taken  not  to  drop  seeds  at  planting  time  in  other  than  the 
hills  marked  out.  These  were  covered  carefully  and  after  the 
young  plants  appeared  above  the  surface,  any  individuals 
not  exactly  in  the  hill  were  removed.  No  plants  have  ever 
given  evidence  that  they  were  misplaced  and  there  is  every 
reason  to  believe  that  the  work  is  accurate  in  this  regard. 

The  different  families  were  marked  in  the  field  by  heavy 
stakes  to  which  wired  tree  labels  were  attached.  As  an  addi- 
tional precaution  against  mis-labeling  or  misplacement  of 
labels,  however,  a  planting  plan  was  always  kept  on  file  showing 
the  exact  location  of  every  plant  in  the  field.  With  this  safe- 
guard every  field  stake  might  have  been  removed  without 
making  the  least  confusion. 

All   crossing   and   selfing    were    done   by   hand.     Individual 


30  INHERITANCE  IN  MAIZE. 

plants  were  used  as  the  male  parent  in  nearly  every  case.  If 
possible  the  male  parent  of  a  cross  was  also  selfed  with  its  own 
pollen  so  that  selfed  seed  of  that  individual  was  accessible  if 
necessary.  If  for  any  reason  it  was  particularly  desirable  to 
have  the  progeny  of  a  plant  where  through  an  accident  none 
of  its  own  pollen  was  available,  it  was  pollinated  from  a  sister 
plant.  This  fact  was  always  noted,  however,  and  the  male 
parent  selfed  if  possible. 

Heavy  manila  paper  bags  were  used  to  protect  both  male  and 
female  inflorescences  from  foreign  pollen.  These  were  found 
much  more  desirable  than  paraffined  bags  as  the  latter  were 
likely  to  become  inverted  and  filled  with  water  during  a  rain 
storm.  The  manila  bags  stood  up  well  in  the  rain,  dried  out 
quickly,  and  seldom  failed  to  furnish  dry  viable  pollen.  The 
tassels  were  bagged  about  three  days  before  any  pollen  was 
ripe.  Of  course  here  there  was  a  slight  chance  of  enclosing 
foreign  poUen.  This  pollen,  however,  would  have  been  three 
or  more  days  older  than  the  pollen  coming  from  the  bagged 
flowers,  and  therefore  much  less  viable.  Even  disregarding 
this  fact,  however,  the  immense  amount  of  pollen  furnished 
by  the  bagged  infloresence  would  so  dilute  any  foreign  pollen 
that  the  ratio  would  be  at  least  10,000  to.  1  in  favor  of  the  former. 

The  female  flowers  were  always  bagged  of  course  before  any 
of  the  silks  were  showing,  and  any  bracts  or  leaves  showing 
foreign  pollen  were  carefully  removed.  Here  again,  however, 
is  a  slight  chance  of  enclosing  foreign  pollen.  This  error  has 
been  determined  by  bagging  53  ears  and  allowing  them  to  re- 
main in  the  bags.  Forty-four  ears  formed  no  seeds,  six  ears 
formed  one  seed  each,  two  ears  formed  two  seeds  each  and  one 
ear  formed  four  seeds.  There  are  over  five  chances  to  one 
then  that  no  viable  foreign  pollen  enters  in  this  way. 

The  pollination  is  accomplished  by  removing  the  bag  from 
the  tassel,  shaking  out  the  empty  anthers  and  dusting  the  pollen 
over  the  silks  of  the  proposed  mother  plant.  The  bag  covering 
the  silks  is  not  entirely  removed  but  is  held  so  that  its  opening 
is  horizontal  with  the  silks  resting  inside.  The  pollen  is  then 
shaken  in  at  the  opening  as  quickly  as  possible,  taking  care 
not  to  let  the  silks  touch  the  hands  or  clothing  of  the  operator 
or  the  leaves  or  stem  of  the  plant.  It  is  sometimes  impossible 
to  keep  from  touching  the  silks  with  the  fingers,  as  it  may  be 


EXPERIMENTAL  ERROR.  31 

necessary  to  rearrange  them  in  the  bag.  To  guard  against 
contamination  from  this  source  the  hands  are  carefully  cleaned 
with  95  per  cent,  alcohol  after  each  pollination. 

The  silks  at  the  base  of  the  ear  mature  first ;  those  at  the  tip 
of  the  ear  last.  For  this  reason,  if  one  is  to  be  absolutely 
certain  of  a  well  filled  ear,  it  is  necessary  to  pollinate  two  or 
three  times  with  fresh  pollen.  This  procedure  has  the  disad- 
vantages of  increasing  the  error,  however,  not  to  speak  of  the 
difficulty  of  obtaining  pollen,  so  that  in  this  work  but  one 
pollination  was  made  in  each  case.  When  pollinated  about 
five  days  after  bagging,  fairly  well  filled  ears  were  generally 
obtained,  particularly  with  the  small  races. 

Immediately  after  pollination  the  ear  is  rebagged  and  tagged. 
From  this  time  until  the  ears  are  mature  they  are  inspected 
every  little  while  to  see  that  the  bags  are  not  too  tight  for  the 
maturing  seeds.  The  bags  remain  on  until  the  ears  are  har- 
vested. They  are  then  picked,  husked,  tagged  with  wired 
tree  labels  and  dried.  Boards  through  which  wire  nails  have 
been  driven  are  hung  from  the  ceiling  of  the  drying  room  to 
prevent  the  depredations  of  mice.  The  ears  are  impaled  upon 
these  nails  and  thus  dry  surrounded  by  a  current  of  air. 

Experimental  Error. 

The  manipulation  during  pollination  is  undoubtedly  pro- 
ductive of  an  experimental  error  which  even  the  most  careful 
work  cannot  entirely  prevent.  This  error  was  determined  as 
follows.  Twenty-five  ears  were  bagged  and  allowed  to  remain 
in  this  condition  for  five  days.  The  bags  were  then  opened 
and  given  the  manipulation  that  was  necessary  for  hand- 
pollination,  except  that  no  pollen  was  applied.  The  ears  were 
then  rebagged  and  remained  so  until  harvest  time.  No  seed 
were  formed  on  sixteen  ears;  three  ears  produced  one  seed 
each ;  four  ears  produced  two  seeds  each ;  while  one  ear  produced 
four  seeds  and  one  ear  produced  five  seeds. 

There  is  a  possibility  then  of  an  experimental  error  of  five  or 
six  seeds  out  of  the  two  hundred  to  eight  hundred  produced 
per  ear.  This  is  to  be  considered  as  a  maximum  error  and 
not  the  probable  error,  the  latter  being  less  than  one  seed  per 
ear. 


INHERITANCE  IN  MAIZE. 


PART  II. 


ENDOSPERM    CHARACTERS. 


These  hybridization  studies  are  all  reported  under  the  head- 
ings of  the  different  characters  investigated,  as  this  seems  to  be 
the  method  calculated  to  show  the  data  with  the  least  con- 
fusion. The  female  parent  is  written  first,  using  the  variety 
number  given  under  the  description  of  the  material  under 
investigation.  For  example  7  x  54  represents  a  cross  of  Learning 
yellow  dent  female  with  Black  Mexican  sweet  male.  When 
this  cross  is  grown  and  hand-pollinated  selfed  ears  are  obtained, 
they  are  numbered  (7  x  54)-l,  (7  x  54)-2,  (7  x  54)-3,  etc.  Should 
ear  number  2  be  grown  for  still  another  generation,  the  crop 
obtained  is  numbered  (7  x  54)-2-l,  (7  x  54)-2-2,  etc.,  thus  the 
exact  generation  of  a  particular  ear  is  always  shown.  The 
characters  under  consideration  are  known  by  letters;  '5',  for 
example  means  presence  of  starchy  character  and  's',  absence 
of  starchy  character:  'P' ,  represents  presence  of  purple  aleurone 
cells;  'p' ,  its  absence.  An  ear  numbered  (7  x  o4)-2-l  P  S 
represents  an  ear  of  the  third  or  Fs  generation  from  Avhich 
purple  starchy  seeds  have  been  selected  for  planting. 

Starchiness  and   Non-starchiness. 

Starchiness  is  the  condition  of  the  endosperm  of  all  of  Sturte- 
vant's  maize  varieties  except  Zea  mays  saccharata,  regardless 
of  the  physical  condition  —  corneous  starch  or  soft  starch  — 
in  which  it  appears.  The  starch  grains  are  fully  developed 
and  possess  a  shape  characteristic  of  the  species  Zea  mays. 
The  sugar  maize  does  not  have  the  ability  to  develop  these 
starch  grains  to  maturity.  Some  starch  is  formed  but  it  remains 
small,  angular  and  abortive,  hence  the  seeds  ripen  from  the 
stage  of  maturity  called  the  "milk"  without  much  change, 
giving  the  seed  a  wrinkled  translucent  appearance.  The  dif- 
ference in  size  of  the  starch  grains  in  the  two  races  is  shown  in 
Table  10.      This  difference  in  the  size  of  starch  grains  however, 


PLATE     II. 


5- 


.->r% 


No.  2'4  Rhode  Island  white  cap  (starchy  parent)  ;  b.  No.  53  Crosby 
non-starchy  parent)  ;  c.  result  of  cross  24x53  showing  heterozygous 
seeds  in  which  starchiness  is  completelj^  dominant,  d,  an  ear  with 
F2  seeds  showing  mono-hybrid  segregation.  Lower  row  daughters 
of  d.  E,  f  and  g,  results  from  planting"  starchy  seeds.  One  ear  out 
of  three  is  pure  starchy,     li,  result  from  planting  non-starchy  seeds. 


Segregation  of  Starchines.s  and  Non-starchiness. 


INHERITANCE  OF  STARCHINESS. 


33 


is  not  the  whole  difference  between  starchy  and  non-starchy 
races.  As  the  starchy  races  ripen,  starch  formation  goes  on 
at  a  steady  rate,  while  in  the  non-starchy  races  there  is  an 
actual  breaking  down  of  endosperm  materials  into  cane  sugar 
and  various  hexoses.  This  is  shown  by  determinations  we  have 
made  of  reducing  sugars  in  both  starchy  and  non-starchy 
races  when  both  were  at  the  "milk"  stage  of  maturity.  The 
non-starchy  races  contained  from  one  and  one-fourth  to  two 
and  one-half  as  much  reducing  sugar  as  the  starchy  races. 

Correns  (:01)  has  already  shown  that  starchiness  behaves 
as  a  Mendelian  dominant  allelomorphic  to  its  absence.  Domi- 
nance was  complete,  and  segregation  generally  *  exact  and 
inheritance  discontinuous.  It  is  not  to  confirm  his  work  that 
the  matter  is  taken  up  here,  but  to  consider  other  questions 
to  which  the  data  are  relevant.  These  questions  relate  chiefly 
to  the  mathematical  hypothesis  of  Mendelism,  to  prepotency 
of  individuals,  and  to  gametic  purity.  The  data  from  which 
the  problems  are  discussed  are  not  selected,   but  the  figures 


The  one  exception  was  the  pop  and  sugar  cross  mentioned  later. 


TABLE  1. 

NO.    15   FLINT   STARCHY   X    NO.    54   NON-STARCHY. 


Ear 

No. 

S 

s 

Total 

Ratio 

per  4 

Dev. 

P.  E. 

(15x54 

-1 

135 

48 

183 

2.9508 

1.0492 

0.0492 

0.0864 

(      " 

-2 

253 

85 

338 

2.9944 

1 . 0056 

0.0056 

0.0635 

(      "      ^ 

-3 

150 

42 

192 

3.1248 

0.8752 

0.1248 

0.0843 

(      "      ^ 

-4 

238 

96 

334 

2.8504 

1.1496 

0.1496 

0.0639 

(      "      ^ 

-6 

190 

72 

262 

2.9008 

1.0992 

0.0992 

0.0722 

(      " 

-8 

302 

96 

398 

3.0352 

0.9648 

0 . 0352 

0.0586 

(      "      ^ 

-11 

242 

105 

347 

2.7896 

1.2104 

0.2104 

0.0627 

/       If 

-15 

236 

79 

315 

2.9968 

1 . 0032 

0.0032 

0.0658 

(15x54 

-2-1 

235 

70 

305 

3.0820 

0.9180 

0.0820 

0.0669 

(      "      ^ 

-2-2 

242 

79 

321 

3.0156 

0.9844 

0.0156 

0.0652 

/      «      ' 

-2-3 

248 

66 

314 

3.1592 

0.8408 

0.1592 

0.0659 

(      "      ^ 

-2-4 

227 

68 

295 

3.0780 

0.9220 

0.0780 

0.0680 

(      " 

-2-5 

200 

59 

2.59 

3.0888 

0.9112 

0.0888 

0.0726 

(      " 

-2-6 

182 

74 

256 

2.8436 

1.1564 

0.1564 

0.0730 

^  /      11 

-2-7 

238 

91 

329 

2.8936 

1.1064 

0.1064 

0.0644 

(      " 

-2-8 

195 

58 

253 

3.0832 

0.9168 

0.0832 

0.0734 

(      " 

)-2-9 

162 

38 

200 

3 . 2400 

0.7600 

0 . 2400 

0.0826 

(      " 

1-2-10 

131 

53 

184 

2.8476 

1.1524 

0.1524 

0.0861 

(      " 

)-2-ll 

132 

40 

172 

3.0696 

0.9304 

0.0696 

0.0891 

(      " 

)-2-12 

101 

32 

133 

3.0376 

0.9624 

0.0376 

0.1013 

34  INHERITANCE  IN  MAIZE. 

include  only  about  one-fourth  of  the  hand-pollinated  ears  at 
our  disposal,  belonging  to  the  starchy  and  non-starchy  cross. 
This  number  seemed  sufficient  for  our  purpose,  and  the  segre- 
gating kernels  were  not  counted  on  the  remaining  ears.  It 
should  be  mentioned  however,  that  any  wide  departures  from 
the  normal  on  any  of  the  four  hundred  selfed  heterozygous 
ears  of  this  cross  would  have  been  noted  and  reported  if  such 
had  occurred. 

Dominance  was  found  to  be  complete.  In  no  case  was  there 
the  slightest  difference  between  the  homozygous  and  the  heter- 
ozygous seeds  in  either  outward  appearance  or  in  the  character 
of  the  starch  cells  when  examined  microscopically.  Whatever 
it  is  that  is  brought  in  by  the  starchy  parent  to  cause  starch 
formation  is  sufficiently  active  to  bring  about  complete  change 
when  present  in  one  "dose"  (that  is  from  one  parent).  As  in 
all  endosperm  characters,  when  S  is  the  male  parent  the  starchi- 
ness  appears  in  the  current  generation  so  called,  giving  the 
most  perfect  illustration  of  Xenia  there  is  known.  As  a  matter 
of  fact,  one  is  not  dealing  with  the  current  generation  but  with 
the  Fi  generation,  the  endosperm  being  a  younger  generation 
than  the  plant  which  bears  the  ear.  In  no  case,  in  an  experience 
with  several  thousand  seeds,  did  an  Fi  seed  showing  Xenia 
fail  to  show  a  heterozygous  condition;  nor  did  extracted  reces- 
sives  (sugar  seeds)  of  the  F2  generation  ever  show  a  heter- 
zoygous  condition.  From  this,  one  may  conclude  that  the  second 
male  nucleus  that  fertilizes  the  endosperm  nucleus  always 
bears  the  same  characters  as  the  first  male  nucleus  that  ferti- 
lizes the  embryo  nucleus  or  egg.  Several  heterozygous  seeds 
have  been  found,  however,  that  were  not  completely  starchy, 
but  had  developed  bilaterally  into  half  starchy  and  half  non- 
starchy.  There  was  not  a  gradual  change  from  the  one  condi- 
tion to  the  other,  but  a  distinct  line  of  demarkation,  with  one 
side  as  absolutely  distinct  from  the  other  as  are  the  pure  races 
of  each  kind.  None  of  these  seeds  were  homozygous  starchy, 
and  Correns'  interpretation  of  similar  phenomena  as  cases  in 
which  the  second  male  nucleus  did  not  fuse  with  the  endosperm 
nucleus  but  each  developed  separately,  seems  well  founded. 
Attention  is  called  to  the  matter  for  this  reason.  It  is  an 
hypothesis  generally  received  with  quiescence  if  not  with 
acquiescence,  that  starchiness  (and  other  "presence"  characters) 


INHERITANCE  OF  STARCHINESS. 


35 


is  due  to  presence  of  an  enzyme  not  possessed  by  the  allelo- 
morph. Now  if  this  is  true,  the  enzyme  must  be  a  colloid  with 
such  large  molecules  that  there  is  absolutely  no  dialysis,  other- 
wise it  seems  as  if  it  would  diffuse  through  the  unripe  seed 
sufficiently  to  act  as  a  catalyser  throughout  the  entire  endo- 
sperm. No  matter  what  is  the  correct  interpretation,  there 
is  certainly  a  definite  chain  of  hereditary  transmission  of  char- 
acters from  cell  to  cell  during  development,  and  each  original 
cell  follows  an  inertia  of  its  own  with  little  influence  on  others. 


TABLE  2. 

NO.   24,   FLINT   STARCHY   X   NO.   54,    NON-STARCHY. 


Ear  No. 

S 

5 

Total 

Ratio  per  4 

Dev. 

P.  E. 

(24  X  54)-l 

274 

94 

368 

2.9784  :  1.0216 

0.0216 

0.0609 

(   "   )-2 

219 

73 

292 

3 . 0000  :  1 . 0000 

0.0000 

0.0684 

(   "   )-6 

256 

89 

345 

2.9680  :  1.0320 

0.0320 

0.0629 

(   "   )-8 

200 

64 

264 

3.0304  :  0.9696 

0.0304 

0.0719 

(   "   )-9 

155 

69 

224 

2.7680  :  1.2320 

0.2320 

0.0781 

(  "  )-io 

212 

59 

271 

3.1292  :  0.8708 

0.1292 

0.0710 

(   "   )-ll 

213 

77 

290 

2.9380  :  1.0620 

0.0620 

0.0686 

(   "   )-12 

268 

80 

348 

3.0804  :  0.9196 

0.0804 

0.0626 

(   "   )-13 

264 

106 

370 

2.8540  :  1.1460 

0.1460 

0.0607 

(   "   )-14 

227 

90 

317 

2.8644  :  1.1356 

0.1356 

0.0656 

(24  X  54)-l-2 

207 

68 

275 

3.0108  :  0.9892 

0.0108 

0.0704 

(   "   )-l-6 

223 

75 

298 

2.9932  :  1.0068 

0.0068 

0.0677 

(   "   )-l-8 

235 

90 

325 

2.8924  :  1.1076 

0.1076 

0.0648 

(   "   )-l-9 

106 

36 

142 

2.9860  :  1.0140 

0.0140 

0.0980 

We  have  said  that  dominance  appears  to  be  complete;  segre- 
gation also  appears  to  be  complete.  It  is  seldom  necessary  to 
subject  extracted  recessives  to  proof  by  growing  them  a  further 
generation.  Some  strains  of  non-starchy  maize,  No.  18  for 
example,  are  much  less  wrinkled  than  others;  and  when  such 
a  strain  is  crossed  with  a  flint  type  there  is  less  difference 
between  dominants  and  recessives  in  appearance  than  when 
certain  other  types  are  crossed.  But  in  no  case  is  there  the 
least  difficulty  in  separating  the  segregates  correctly.  Whether 
this  apparent  segregation  is  as  complete  as  it  appears^  we  shall 
discuss  presently.  It  should  further  be  mentioned  that  the 
seeds  can  also  be  classified  with  absolute  exactness  by  micro- 
scopical examination. 


36 


INHERITANCE  IN  MAIZE. 


Tables  1-9  contain  the  proportion  of  the  starchy  and  non- 
starchy  seeds  obtained  as  progeny  when  heterozygous  seeds 
were  planted;  although,  as  was  stated  before,  only  a  few  ears 
from  each  family  were  counted.  One  object  in  view  is  to  show 
the  behavior  of  starchy  and  non-starchy  in  several  races. 

TABLE  3. 

NO.    5,    FLINT   STARCHY   X    NO.    18,    NON-STARCHY. 


Ear  No. 


5  X  18)-4 

"  )-8 

"  )-10 

"  )-16 

"  )-18 

"  )-21 

"  )-25 

"  )-30 


s 

5 

Total 

181 

68 

249 

172 

66 

238 

215 

68 

283 

225 

69 

294 

186 

61 

247 

136 

42 

178 

176 

50 

226 

218 

68 

286 

Ratio  per  4 


2.9176  :  1.0924 
2.9908  :  1.1092 
3.0388 


3.0612 
3.0120 
3 . 0560 
3.1152 
3.0488 


0.9612 
0.9388 
0.9880 
0 . 9440 
0.8848 
0.9512 


Dev. 


0 . 0924 
0.1092 
0.0388 
0.0612 
0.0120 
0.0560 
0.1152 
0.0488 


P.  E. 


0 . 0740 
0.0757 
0.0694 
0.0681 
0.0743 
0.0876 
0.0777 
0.0691 


There  is  reason  to  believe  that  different  races  can  be  identical 
in  appearance,  but  may  have  such  different  gametic  composition 
that  they  may  affect  a  character  possessed  by  a  race  with  which 
they  may  be  crossed,  in  very  different  manners.  (See  purple 
aleurone  cells  and  non-purple.)  Examination  of  the  tables 
shows  this  not  to  be  the  case  with  starchy  and  non-starchy. 
All  of  the  starchy  and  non-starchy  races  with  which  crosses 
have  been  made  behave  in  exactly  the  same  manner.  There 
is  no  difference  in  appearance  in  heterozygotes  from  different 
races  that  is  not  accounted  for  by  the  different  shaped  seeds 
possessed  by  the  parents,  and  wide  variations  in  shape  occur 
only  in  generations  later  than  Fi.  In  the  Fi  generation  the 
shape  is  intermediate  between  that  of  the  two  parents. 

TABLE  4. 

NO.    11,   FLINT   STARCHY  X   NO.    18,   NON-STARCHY. 


Ear  No. 

S 

J 

Total 

Ratio  per  4 

Dev. 

P.  E. 

(11  X  18)-7 
(      "      )-14 
(      «      )-15 
(      «      )-22 

220 
218 
200 
235 

74 
81 

77 
87 

294 
299 

277 
322 

2.9932  :  1.0068 
2.9164  :  1.0836 
2.8880  :  1.1120 
2.9192  :  1.0808 

0.0068 
0.0836 
0.1120 
0.0808 

0.0681 
0.0676 
0.0702 
0.0651 

INHERITANCE  OF  STARCHINESS.  ,  37 

If  one  examines  the  tables  carefully  however,  he  sees  at  once 
that  there  is  quite  a  difference  in  the  ratios  obtained.  They 
vary  from  a  ratio  of  2.7896  :  1.2104  in  ear  (15  x  54)-ll,  Table 
1  to  a  ratio  of  3.2020  :  0.7980  in  ear  (19  x  7) -2,  Table  7.  This 
brings  up  an  important  question.  Does  this  discrepancy 
represent  an  expected  probable  error  in  chance  matings;  or,  is 
there  a  prepotency  in  certain  families  through  which  excessive 
numbers  of  dominants  or  of  recessives  tend  constantly  to 
reappear?  Correns  did  indeed  find  in  one  family  such  an  excess 
of  starchy  seeds,  but  it  is  not  known  whether  this  apparent 
prepotency  was  transmitted  in  further  generations. 

Tables  1-9  show  several  cases  where  ears  with  a  ratio  deviat- 
ing from  the  expected  3  :  1  of  Mendelian  hypothesis  have  been 
grown  for  another  generation.  For  example,  ear  (8  x  54)-l 
of  Table  6  has  a  ratio  of  2.9420  :  1.0580  while  ear  (8  x  54)-5 
of  the  same  table  has  a  ratio  of  3.0780  :  0.9220;  yet  the  progeny 
of  these  ears  average  just  about  the  3  :  1  ratio  of  theory.  There 
are  even  more  ears  with  an  excess  of  recessives  from  the  ear 
that  had  the  excess  of  dominants  and  vice  versa.  Other  deviants 
have  been  grown  for  several  generations,  and  while  the  exact 
ratios  have  not  been  recorded  it  may  be  stated  with  confidence 
that  wide  deviations  occurring  in  considerable  numbers  would 
have  been  noticed  while  making  other  records.  It  may  be 
concluded  then  that  no  prepotency  or  tendency  to  aberrant 
ratios  is  a  constant  characteristic  of  any  of  our  families.  How 
then  can  the  discrepancies  from  theoretical  ratios  be  explained? 

To  study  this  question  the  probable  errors  of  all  of  the  ratios 
have  been  calculated.  The  method  used  has  been  that  of 
Johannsen  (:  09,  p.  405),  except  that  the  mean  error  has  been 
reduced  to  the  probable  error  by  multiplying  by  the  factor 
0.6745.     The  standard  deviation  of  a  Mendelian  proportion  is 


VpXq 
=t where  p  and  q  are  the  Mendelian  terms,  in  this  case 

p+q 


-\/3Xl  1.7321 

case  3  and  1.   Thens.D.=  ± =± =±0.4330.   The 

4  4 

S.  D. 

probable  error,  E=  ±0.6745 where  n  is  the  total  number 

of  variates. 


38  INHERITANCE  IN  MAIZE. 

To  find  out  whether  the  different  ratios  given  in  Tables  1-9 
are  what  should  reasonably  be  expected  if  the  Mendelian 
theory  of  chance  matings  of  equal  numbers  of  gametes  5  and  5 
in  both  male  and  female  germ-cells  is  correct,  it  should  be  under- 
stood just  what  is  meant  by  probable  error  in  the  law  of  error. 
Plus  errors  and  minus  errors  should  occur  with  equal  frequency, 
small  errors  should  occur  more  frequently  than  large  errors, 
and  very  large  errors  should  not  occur.  Determined  as  above 
the  probable  error  means  that  the  chances  are : 

1  to  1  that  the  true  value  lies  within  =>=  E 

4 . 5  to  1  that  the  true  value  lies  within  ±  2E 

21  to  1  that  the  true  value  lies  within  ±  3E 

142  to  1  that  the  true  value  lies  within  ±  4E 

The  theory  of  error  also  provides  for  errors  of  any  size  in  their 
proper  frequency  or  rather  infrequency,  but  as  a  matter  of 
fact  in  practice  if  errors  greater  than  ±  4E  occur  they  are 
probably  due  to  experimental  errors  or  avoidable  mistakes. 

We  may  consider  each  ear  given  in  Tables  1-9  as  a  determi- 
nation and  its  probable  error  as  the  probable  error  of  a  single 
determination.  With  this  in  mind  we  find  that  in  the  94  ears 
tabled  there  are  49  plus  errors  and  45  minus  errors.  Further 
we  find  that  the  theoretical  mode  or  0  error  is  almost  3:1, 
being  in  fact  very  slightly  greater.  The  errors  are  distributed 
as  follows : 

Within  ±  E  47 . 8%  —  Theory  50 . 0% 
Within  ±  2  E  83 . 0%  —  Theory  82 . 3% 
Within  ±  3  E  96 . 8%  —  Theory  95 . 7% 
Within  ±  4  E  100 . 0%  —  Theory  99 . 3% 

The  sum  total  of  these  segregates  is  23529  to  7811,  a  ratio  of 
3.0031  :  0.9969  ±  .0066. 

It  should  be  mentioned  simply  in  order  to  suppress  no  data 
that  one  ear  was  found  with  a  probable  error  somewhat  in 
excess  of  ±  4  E.  It  was  found  by  growing  this  ear  for  another 
generation  however  that  this  was  due  to  an  experimental  error. 
There  was  a  great  excess  of  sugar  seeds,  but  in  the  starchy 
seeds  there  proved  to  be  about  4  heterozygotes  to  1  homozy- 
gote.  Since  no  other  ear  like  this  has  ever  been  obtained,  and 
since  it  is  known  that  during  the  progress  of  this  experiment 


INHERITANCE  OF  STARCHINESS. 


39 


several  ears  were  first  selfed  with  pollen  killed  by  rain  and 
afterward  pollinated  with  pollen  from  a  sugar  plant  to  get 
material  for  another  purpose,  it  seems  highly  probable  that  this 
ear  was  of  a  similar  mixed  parentage  and  that  its  explanatory 
label  had  been  lost. 

As  to  whether  these  data  support  the  Mendelian  h3qDothesis 
or  not  there  may  be  slight  grounds  for  a  difference  in  opinion. 
Our  own  opinion  is  that  when  we  take  into  consideration  the 
chance  for  experimental  error,  the  ratios  are  well  within  the 
limits  of  probable  error.  One  thing  at  least  is  brought  out  clearly, 
the  behavior  of  segregates  in  more  than  one  generation  and  a 
variety  of  matings  are  necessary,  if  one  is  to  draw  conclusions 
as  to  the  exact  mode  of  inheritance  of  character  pairs  from 
small  numbers. 

One  further  point  remains  for  discussion.  Do  the  extracted 
homozygotes  breed  true  ?  In  other  words,  is  segregation  an 
absolute  separation  of  a  gene  from  its  absence  ?  or,  is  there  only 
a  relative  segregation?  Morgan  (;  10)  has  suggested  that 
relative  segregation  may  explain  Mendelian  facts,  if  one  pre- 
supposes that  when  the  amount  of  the  gene  falls  below  a  certain 
limit  the  dominant  fails  to  develop.  This  idea  while  interpret- 
ing the  facts  in  the  F2  generation  is  inadequate  to  explain  the 
apparent  purity  of  further  generations  of  extracted  recessives, 
for  if  this  hypothesis  were  true  many  recessives  would  show  the 
dominant  character  when  crossed. 

In  Table  9  is  shown  the  segregation  of  extracted  dominant 
starchy  seeds.  The  ratio  is  as  nearly  the  expected  2  hetero- 
zygotes  to  1  homozygote  as  could  well  be  expected.     Several 


TABLE  5. 

NO.    17,  FLINT  STARCHY  X  NO.   54,   NON-STARCHY;     NO.   18,  NON-STARCHY  X 
NO.    58,    FLINT   starchy;      and    NO.    7,    DENT   STARCHY   X    NO.    54, 

NON-STARCHY. 


Ear  No. 

S 

5 

Total  ;        Ratio  per  4 

1 

Dev. 

P.  E. 

(17  X  54)-l 
(18  X  58)-l 
(  7  X  54)-l 
(      "      )-2 

328 
332 
379 
493 

102 
102 
137 
131 

430 
434 
516 

624 

3.0512  :  0.9488 
3.0600  :  0.9400 
2.9380  :  1.0620 
3.1604  :  0.8396 

0.0512 
0 . 0600 
0.0620 
0.1604 

0.0563 
0.0561 
0.0514 
0.0467 

40  INHERITANCE  IN  MAIZE. 

thousand  dominant  homozygotes  have  been  bred  for  further 
generations  and  these  have  all  bred  true  to  the  starchy  character. 
This  is,  in  general,  the  case  with  the  extracted  non-starchy 
seeds.  Furthermore,  there  are  in  commercial  use  many  sugar 
corns  that  are  extracted  recessives.  Golden  Bantam,  Late 
Egyptian  and  many  others  are  examples  of  races  that  have 
originated  from  crosses  with  starchy  varieties.  The  wrinkled 
seeds  have  been  selected  and  have  bred  true.  Out  of  the  many 
million  seeds  that  are  annually  grown  for  the  canning  factories, 
however,  there  does  appear  an  occasional  ear  with  semi-starchy 
seeds.  These  ears  transmit  the  character  and  give  the  canners 
no  end  of  trouble.  There  is  no  way  to  find  out  whether  these 
ears  appear  only  on  varieties  which  somewhere  in  their  ancestry 
had  a  starchy  parent.  One  can  only  say  that  they  do  appear 
in  ratios  not  exceeding  one  ear  in  ten  thousand.  By  some 
lucky  chance  some  of  these  ears  made  their  appearance  in  our 
controlled  cultures.  All  of  our  extracted  recessives  have 
proved  true  to  non-starchiness  (*)  except  from  the  progeny  of 
ear  (8  x  54) -1-6.  The  majority  of  the  progeny  of  this  ear  were 
also  non-starchy,  but  three  ears  appeared  which  were  decidedly 
semi-starchy,  one  of  which  is  shown  in  Plate  III,  fig.  b.  There 
was  no  possibility  that  these  ears  could  have  grown  from  a 
normal  heterozygous  seed.  They  were  not  plump  seeds  like 
a  true  heterozygote  nor  did  they  segregate  into  starchy  and 
non-starchy  in  the  next  generation.  The  entire  ear  was  rather 
uniformly  semi-starchy  and  quite  different  from  the  true  starchy 
ears.  Microscopical  examination  showed  definitely  that  starch 
grains  had  been  developed  normally  to  a  size  intermediate 
between  the  true  starchy  and  the  true  sweet  seeds  of  the  same 
family.     This  fact  is  shown  in  Table  10. 


*  There  are  other  cases  where  some  apparent  starchiness  is  always 
developed,  namely  when  pop  races  are  crossed  with  non-starchy  races. 
We  interpret  this  as  being  due  to  the  small  size  of  the  resulting  F2  seeds 
borne  on  intermediate  Fi  ears.  When  the  seeds  are  small  the  endosperm 
material  more  nearly  fills  the  pericarp  than  when  they  are  large.  The 
wrinkled  condition  is  therefore  less  apparent.  If  one  has  had  consider- 
able experience  in  classifying  starchy  and  non-starchy  seeds,  such  crosses 
are  seen  to  show  normal  segregation.  If,  however,  careful  classification 
is  not  made  and  the  seeds  are  not  tested  in  further  generations  pop  and 
non-starchy  crosses  always  appear  to  show  an  excess  of  starchy  seeds. 
It  is  suggested  that  this  is  the  explanation  of  Corren's  failure  to  obtain 
normal  ratios  in  a  similar  cross.  These  cases  are  not  real  exceptions 
to  the  statement  made  above,  however,  for  recessives  extracted  from  pop 
crosses  are  never  grown  commercially  as  sugar  corns. 


PLATE    III. 


.^'w'^j.'Ct-*^^x^j.\'ii-yi- 


a.     P2,  Fi,  and  F2  seeds  from  cross  between  No.  19  Stowell's  Evergreen 
sugar  and  No.  2  Illinois  low  protein  dent  maize. 


b.  Middle  ear  is  a  semi-starchy  ear  No.  (8x54) -1-6,  progeny  of  an  ex- 
tracted recessive  (wrinkled)  seed.  On  the  left  is  an  extracted  dom- 
inant (starchy)  ear  of  the  same  cross.  On  the  right  is  a  well 
wrinkled  ear,  sister  of  No.   (8x54) -1-6. 

Segregation  of  Starchiness  and   Non-Starchiness. 


PLATE    IV. 


a      Random   sample   of   progeny   of   starchiest  seeds   of   semi-starch}^    ear 
shown  in  Plate  III. 


b.     Random  sample  of  progeny  of  most  wrinkled  seeds  of  semi-starch}' 
ear  shown  in  Plate  III. 


Gametic   Purity. 


INHERITANCE  OF  STARCHINESS. 


41 


TABLE  6. 

NO.    8,    DENT   STARCHY   X   NO.   54,    NON-STARCHY. 


Ear  No. 

S 

.J 

Total 

Ratio  per  4 

Dev.       P.  E. 

(8  X  54)-l 

(     "      )-2 
(     "      )-3 
(     "      )-5 

381 
340 
400 

384 

137 
137 
141 
115 

518 
477 
541 
499 

2.9420  :  1.0580 
2.8512  :  1.1488 
2.9576  :  1.0424 
3.0780  :  0.9220 

0.0580  0.0513 
0.1488  i  0.0535 
0.0424  0.0502 
0.0780    0.0523 

(8  X  54)-l-3PC 
(     "      )-l-4PC 
(     "      )-l-6PC 
(     "     )-l-8PC 
(     "     )-l-14PC 
(     "     )-l-6P 
(     "     )-l-llP 
(     "     )-l-13P 
(     "     )-l-15P 
(     "     )-l-l 
(     "     )-l-2 
(     "      )-l-4 
(     "      )-l-10 
(     "      )-l-29 

243 
302 
231 
321 
238 
145 
268 
320 
293 
237 
236 
176 
242 
272 

236 
294 
147 
277 
357 
324 
306 
249 

64 

105 

81 

117 

66 

40 

78 

107 

96 

88 

88 

60 

80 

93 

307 
407 
312 
438 
304 
185 
346 
427 
389 
325 
324 
236 
322 
365 

3.1660  :  0.8340 
2.9680  :  1.0320 
2.9616  :  1.0384 
2.9316  :  1.0684 
3.1316  :  0.8684 
3.1356  :  0.8644 
3.0984  :  0.9016 
2.9976  :  1.0024 
3.0128  :  0.9872 
2.9168  :  1.0832 
2.9136  :  1.0864 
2.9832  :  1.0168 
3.0064  :  0.9936 
2.9808  :  1.0192 
2.8956  :  1.1044 
2.9924  :  1.0076 
2.8268  :  1.1732 
3.1748  :  0.8252 
2.9748  :  1.0252 
2.9932  :  1.0068 
3.1304  :  0.8696 
2.9732  :  1.0268 

0.1660  0.0667 
0.0320  0.0579 
0.0384  ,  0.0672 
0.0684  0.0558 
0.1316  0.0670 
0.1356  0.0859 
0.0984  i  0.0628 
0.0024  0.0565 
0.0128  0.0592 
0.0832  0.0648 
0.0864  0.0649 
0.0168  0.0760 
0.0064  0.0651 
0.0192    0.0611 

(8  X  54)-5-2 
(     "      )-5-3 
(     "      )-5-4 
(     "      )-5-5      • 
(     "     )-5-6 
(     "     )-5-8 
(     "     )-5-10 
(     "     )-5-ll 

90 
99 
61 
72 
123 
109 
85 
86 

326 
393 
208 
349 
480 
433 
391 
355 

0.1044  0.0647 
0.0076  0.0589 
0.1732  0.0810 
0.1748  0.0625 
0.0252  0.0533 
0.0068  0.0651 
0.1304  0.0591 
0.0268    0.0638 

Seeds  from  the  ear  shown  in  Plate  III,  fig.  b,  were  divided 
into  two  classes,  those  most  nearly  starchy  and  those  most 
nearly  non-starchy,  and  planted.  A  number  of  selfed  ears 
were  obtained  from  each  class.  Those  resulting  from  the  seeds 
most  nearly  non-starchy  were  in  part  what  would  immediately 
be  classified  as  non-starchy  and  in  part  as  starchy  in  appearance 
as  the  parent  ear.  The  ears  resulting  from  the  seeds  most 
nearly  starchy  were  all  as  starchy  as  the  parents  and  certain 
of  them  even  more  so.  This  fact  is  shown  in  Plate  IV.  Micro- 
scopical examination  of  the  most  starchy"  seeds  of  this  genera- 
tion showed  that  the  starch  grains  were  most  of  them  developed 
to  normal  size.  The  ears  were  not  uniform  nor  was  there 
uniform  starchiness  among  the  seeds  of  a  single  ear.  Seeds  could 
be  selected  which  formed  a  series  running  from  true  sweet  to 
true  starchy,  yet  those  most  nearly  starchy  had  a  rough  appear- 


42 


INHERITANCE  IN  MAIZE. 


TABLE  7. 

NO.   19,   NON-STARCHY  X  NO.   7,   DENT  STARCHY  AND  NO.   19,   NON-STARCHY 
X   NO.   8,   DENT   STARCHY. 


Ear  No. 

S 

s 

Total 

Ratio  per  4 

Dev. 

P.  E. 

(19x7)-2. 

(  "  )-5 

297 
486 

74 
156 

371 
642 

3.2020  :  0.7980 
3.0280  :  0.9720 

0.2020 
0.0280 

0.0607 
0.0461 
0.0575 

(19  x  7)-5-l 

304 

109 

413 

2 . 9444  :  1 . 0556 

0.0556 

(19x8)-l 
(   "   )-2 
(  "  )-3 

(  "■  )-4 
(  "  )-5 

183 
464 
449 
303 
414 

64 
152 
151 

96 
139 

247 
616 
600 
399 
553 

2.9636  :  1.0364 
3.0128  :  0.9872 
2.9932  :  1.0068 
3.0376  :  0.9624 
2.9948  :  1.0052 

0.0364 
0.0128 
0.0068 
0.0376 
0.0052 

0.0743 
0.0471 
0.0477 
0.0585 
0.0507 

ance  very  different  from  the  well-filled  pericarp  of  the  true 
starchy  seeds  of  the  same  family.  These  seeds  will  be  selected 
for  Starchiness  and  if  uniform  ears  are  finally  obtained,  will 
be  crossed  with  non-starchy  again  to  see  if  their  behavior 
is  the  same  as  normal  starchy  maize.  Provisionally  one  is 
forced  to  one  of  two  conclusions.  Either  homozygous  reces- 
sive s  {and  likewise  dominants)  are  not  complete  segregates,  but 
products  of  a  partial  quantitative  separation  of  genes  allowing 
traces  of  the  dominant  character  to  remain,  traces  which  may 
sometimes  accumulate  sufficiently  to  bring  out  the  dominant 
character:  or,  progressive  variations  are  constantly  taking  place 
in  small  numbers,  'most  often  along  paths  that  have  been  passed 
before. 


TABLE  8. 

NO.    60,    POP   STARCHY   X   NO.    54,    NON-STARCHY. 


Ear  No. 

S 

s 

Total 

Ratio  per  4   i  Dev.    P.  E. 

(60-5  X  54)-2 
(    "    )-6 
(    "    )-8 
(    "   )-ll 
(    "    )-12 

274 
273 
163 
191 
249 
296 
260 
243 

82 

102 

53 

58 
84 

356 
375 
216 
249 
333 

3.0788  :  0.9212  0.0788   0.0619 
2.9120:1.0880  0.0880   0.0603 
3.0184  :  0.9816   0.0184   0.0795 
3.0684:0.9316   0.0684   0.0740 
2.9908:  1.0092   1.0092   0.0640 

(60-3  X  54)-l 
(    "    )-5 
(    "    )-6 

87 

107 

73 

383  1  3.0912:0.9088   0.0912   0.0597  \ 
367   2.8336  :  1.1664   0.1664   0.0610  ! 
316  1  3.0760:0.9240  0.0760   0.0657 

(60-8  X  54)-l 
(    "    )-8 

227 
224 

67 
71 

294  3.0884  :  0.9116 

295  3.0372:0.9628 

0.0884   0.0681 
0.0372   0.0680 

INHERITANCE  OF  STARCHINESS.  43 

It  is  our  opinion  that  dominant  starchiness  —  if  it  is  the 
same  dominant  starchiness  —  has  been  formed  anew.  It 
occurs  too  rarely  to  support  a  partial  segregation  theory  such 
as  Morgan's  (:  10).  If  it  is  asked  why  starchiness  is  the  char- 
acter that  arises  anew  rather  than  another  variation,  it  is  sug- 
gested that  the  peculiar  chemical  structure  of  the  germ  cell  of 
maize  may  be  such  that  a  molecular  readjustment  is  much  more 
likely  to  bring  about  starchiness  than  any  other  variation. 
Such  a  path  of  least  resistance  for  variations  might  account  for 
the  many  cases  in  animals  and  plants  where  the  same  variation 
has  apparently  occurred  again  and  again. 

Conchision. 

These  starchy  and  non-starchy  crosses  represent  a  much 
larger  number  of  individuals  than  have  ever  before  been  studied 
in  accurately  controlled  pedigree  cultures.  Taking  them  as  a 
whole  they  show  that  the  mechanism  by  which  the  members 
of  an  allelomorphic  pair  are  distributed  among  the  gametes,  is 
accurate.  The  aberrant  ratios  sometimes  obtained  are  what 
should  be  expected  by  the  Law  of  Error.  They  are  not 
inherited,  and  we  believe  this  to  show  that  there  is  no  such 
thing  as  prepotency  per  se  which  would  cause  abnormal  ratios. 
We  might  extend  this  conclusion  further  and  say  that  there  is 
no  conclusive  evidence  of  a  failure  of  segregation  of  male  gametes 
or  of  selective  fertilization  (Lock  :  06) ,  or  of  partial  gametic 
coupling  that  presupposes  gametes  bearing  opposite  genes  to 
be  formed  in  unequal  numbers  (Bateson  and  Punnett  :  08). 
Disbelief  in  prepotency  of  the  kind  described  above  does  not 
indicate  disbelief  in  different  "potencies"  as  described  by 
Davenport  (:  10).  Different  potencies,  that  is  various  degrees 
of  manifestation  of  the  same  character  due  to  its  modification 
during  development  by  the  action  of  other  developing  genes 
possessed  by  the  individual,  is  a  different  thing  and  is  entirely 
logical.  In  prepotency  or  potency  of  this  kind  segregations 
are  perfectly  normal,  and  modifications  which  occur  in  characters 
are  due  to  the  gametic  constitution  of  the  individual. 

The  aberrant  ratios  obtained  by  Correns  in  the  pop-sugar 
cross  referred  to  above,  may  have  been  due  to  modification  by 
other  unknown   characters   possessed  by   the  parents,   but  it 


44  INHERITANCE  IN  MAIZE. 

seems  more  likely  that  they  were  due  to  improper  classification 
of  dominants  and  recessives  for  the  reason  that  recessives  in 
such  crosses  although  hyaline  and  easily  classified  microscopically 
often  do  fill  the  pericarp  with  endosperm  material  owing  to  the 
small  size  of  the  seed. 

If  then,  in  cases  of  simple  mono-hybrids  where  there  are  no 
complications,  a  ratio  of  3.0031  :  0.9969  ±  .0066  is  obtained; 
are  we  not  compelled  to  take  the  view  that  segregation  occurs 
at  the  reduction  division?  Could  any  less  exact  division  give 
the  distribution  of  genes  necessary  for  such  exact  recombi- 
nations? Of  course  it  has  long  been  suspected  that  this  was 
the  time  of  segregation,  but  Bateson  (:  09  p.  271)  has  felt  that 
obstacles  were  in  the  way  of  interpretiiig  the  chromosomes 
as  such  important  bearers  of  hereditary  qualities.  These 
obstacles  were  three  in  number;  first,  it  is  objected  that  no 
correspondence  has  been  shown  between  visible  differences 
of  type  (except  sex)  and  chromosome  differences;  second,  that 
no  correspondence  between  complexity  of  type  and  chromosome 
numbers  has  been  shown;  and  third,  that  bud  sports  are  somatic 
segregates.  There  are,  it  seems  to  us,  no  real  obstacles  here. 
One  should  expect  that  the  quality  of  the  chromosome  and  not 
shape  or  number,  is  the  important  fact.  It  is  even  likely  that 
most  of  the  important  morphological  characters  are  carried 
by  all  of  the  chromosomes,  hence  a  doubling  of  chromosome 
number  as  has  occurred  in  Oenothera  gigas  may  be  relatively 
unimportant.  The  case  of  bud  sports  is  also  fairly  clear  since 
Winkler  ( :  09)  has  shown  that  a  graft  hybrid  between  the 
black  night  shade  and  the  tomato  proved  to  have  the  sum  of 
the  haploid  numbers  of  the  two  parents  and  not  the  sum  of  the 
diploid  numbers.  The  somatic  cell  then  has  a  regulatory  appa- 
ratus of  its  own.  What  might  be  called  the  normal  bud  sport 
(other  sports  probably  occur  from  abnormal  cell  divisions)  is 
probably  due  to  the  fusion  of  two  somatic  cells  of  a  hetero- 
zygote,  followed  by  a  reduction,  in  which  one  of  the  homozygote 
forms  appears.  It  must  be  not  understood  however  that  be- 
cause Bateson 's  objections  are  considered  surmountable,  we 
therefore  believe  it  to  be  proved  that  the  chromosomes  are  the 
sole  bearers  of  hereditary  characters  and  that  the  reduction 
division  is  the  time  of  Mendelian  segregation.  Judgment 
must  still  be  suspended  on  these  matters. 


INHERITANCE  OF  STARCHINESS. 


45. 


TABLE  9. 

EARS   FROM   F2   GENERATION   PLANTS   OF   STARCHY   AND   NON-STARCHY 

CROSSES. 

Starchy  Seeds  Planted. 


Selection 

Heterozygous  S 

Homozygous  S 

(  8  X  54)-l 

6 

4 

(      "       )-2 

4 

5 

(       "       )-3 

30 

17 

(       "       )-5 

75 

31 

(       "       )-l-l 

67 

32 

(       "       )-l-2 

44 

25 

(      "       )-4 

71 

38 

(     "     )-io 

48 

28 

(15  X  54)-2 

46 

13 

(       "       )-3 

25 

17 

(24  X  54)-l 

.      28 

14 

Total 

444 

224 

Ratio 

1.93 

1 

TABLE  10. 

RANDOM  COMPARISON   OF   DIAMETER   OF   STARCH   GRAINS. 

Extracted  Starchy  Seeds  from  {8  x  54)-i  o,nd  Semi-Starchy  and 
Non-Starchy  from  (8  x  54)— 1—6. 


Diam.  in  mm. 

.009 

.017 

1 

.034 

9 

52 

.052 

.069 

.086 

.103 

.12 

.138 

.155 

Total 

No.  variates 

from  starchy 

seeds 

23 
57 

34 

48 

66 

36 

16 

12 

3 

198 

No.  variates 

from  semi-starchy 

seeds 

17 

17 

11 

5 

227 

No.  variates 

from  non-starchy 

seeds 

34 

94 

52 

13 

193 

46  INHERITANCE  IN  MAIZE. 

Yellow  and  Non-yellow  Endosperm. 

Correns  (:01)  and  Lock  (:06)  each  found  a  yellow  color  in 
the  endosperm  which  behaved  with  its  absence  as  a  single  alle- 
lomorphic  pair.  We  have  found  two  *  yellow  colors  in  the 
endosperm  each  behaving  when  crossed  with  its  absence,  as 
an  independent  allelomorphic  pair.  A  part  of  the  experiments 
with  these  characters  has  been  described  in  a  previous  paper 
(East  :10).     In  this  paper  some  further  data  are  presented. 

Both  of  these  yellow  colors,  although  they  behave  in  inheri- 
tance as  separate  entities  are  either  identical  or  very  similar 
in  composition.  They  are  insoluble  in  water,  somewhat  soluble 
in  alcohol  and  easily  soluble  in  ether,  chloroform,  benzine, 
benzol  and  carbon  bisulphide.  They  occur  in  rhombic  plates 
in  the  starch  cells  and  possibly  also  in  the  chromoplasts  although 
this  is  not  certain.  From  these  facts  it  might  be  supposed  that 
they  were  hydrocarbons  with  compositions  similar  to  carotin. 
They  do  not  give  the  general  reactions  however  which  the  fatty 
pigments  or  lipochromes  - —  of  which  carotin  is  an  example  — 
give  with  sulphuric  acid  or  iodine  dissolved  in  aqueous  potas- 
sium iodide.  Independent  of  their  solubility  reactions,  this 
would  class  them  with  tlie  anthochlorins  (Courchet  '88). 

Considering  the  importance  to  Mendelian  theory  of  the 
discovery  that  two  similar  and  possibly  identical  characters 
may  each  act  with  its  own  absence  as  an  independent  allelomor- 
phic pair,  further  chemical  investigations  are  being  made  which 
will  be  reported  in  a  separate  paper.  It  may  simply  be  stated 
here  that  as  far  as  is  known  these  colors  are  indistinguishable, 
but  as  they  behave  differently  in  crosses  they  will  be  known  as 
Yi  and  Y^. 

~  A  number  of  crosses  were  made  between  yellow  and  non- 
yellow  which  gave  only  3  :  1  ratios.  The  remaining  crosses 
shown  in  Tables  11-16  each  showed  one  or  more  ears  with 
dihybrid  ratios. 


*  Lock  mentioned  that  light  yellow  seeds  appeared  in  his  crosses,  but 
he  classed  them  as  whites  which  vitiates  his  study  of  Mendelian  numerical 
proportions. 


INHERITANCE   OF   YELLOW   ENDOSPERM.  47 

TABLE  11. 

F2   SEEDS   FROM   CROSS   OF   NO.    1    WHITE   DENT   X   NO.   7   YELLOW  DENT. 


Ear  No. 

Y 

y 

Ratio  Approx. 

(1  X  7)-l 
(1  X  7)-2 

587 
127 

212 
30 

3  :  1 
3  :  1 

Table  11  gives  the  results  from  two  selfed  ears  of  No.  1  white 
dent  crossed  with  No.  7  yellow  dent.  They  approximate  3  to  1 
ratios  although  ear  No.  1  has  an  excess  of  non-yellow  and  ear 
No.  2  an  excess  of  yellow  seeds.  This  cross  proved  to  be  too 
late  for  the  Connecticut  climate  and  the  resulting  Fa  seeds  were 
immature  and  difficult  to  classify.  Yellow  was  dominant  and 
appeared  as  Xenia  in  the  Fi  seeds  but  the  F2  seeds  varied  in 
different  ears  in  a  peculiar  manner.  Where  there  was  suffi- 
cient soft  starchy  matter  in  the  caps  of  the  seeds  the  hetero- 
zygotes  were  considerably  lighter  colored  at  the  cap  than  when 
the  seeds  possessed  more  corneous  starch.  The  same  phenome- 
non occurred  in  reciprocal  crosses;  so  that  when  there  was 
sufficient  soft  starchy  matter  the  heterozygotes  could  be  dis- 
tinguished from  the  homozygotes  either  way  the  cross  was  made. 
(See  cross  of  floury  yellow  with  non-yellow.) 

Ear  (1  X  7)-lY  gave  only  one  selfed  ear  with  126  yellows  of 
various  shades,  14  white,  and  3  doubtful  seeds.  The  mother 
seed  was  probably  Yi  Y2  yi  y2.  Several  open  field  ears  from 
yellows  with  white  caps  all  proved  to  be  heterozygous,  thus 
proving  the  above  statement  regarding  Xenia.  The  crop 
from  the  white  seeds  proved  pure  for  non-yellow. 


INHERITANCE  IN  MAIZE. 


TABLE  llA. 

F3  SEEDS  OF  EAR  NO.  2  OF  CROSS  SHOWN  IN  TABLE  11. 

Yellow  Seeds  Planted. 


Ear  No. 

Y 

y 

Ratio  Approx. 

(1  X  7)-2-3 

423 

108 

3  :  1 

'  )-2-7 

351 

108 

3  :  1 

'  )-2-8 

375 

120 

3  :  1 

'  )-2-12 

343 

111 

3  :  1 

'  )-2-14 

577 

Pure  yellow 

'  )-2-17 

286 

'58 

3  :  1 

'  )-2-18 

209 

87 

3  :  1 

'  )-2-19 

360 

135 

3  :  1 

'  )-2-20 

341 

105 

3  :  1 

'  )-2-22 

319 

92 

3  :  1 

'  )-2-23 

408 

168 

3  :  1 

'  )-2-25 

633 

40 

15  :  1 

Table  11a  shows  the  results  from  planting  (1  x  7) -2  Y  seeds. 
Ears  Nos.  3  and  17  have  an  excess  of  yellow  seeds.  Possibly 
they  were  15  :  1  ratios  in  which  the  yellows  were  very  light  and 
could  only  have  been  classified  with  certainty  by  growing  the 
supposed  whites  another  generation.  The  remaining  ears  all 
showed  3  :  1  ratios  except  ear  No.  25.  This  ear  was  clearly 
a  15:1  ratio.  The  crop  from  (1  x  7)-2y  (extracted  whites) 
gave  12  pure  white  ears,  showing  that  the  classification  of  the 
F2  seeds  was  correct. 

A  cross  between  No.  5  white  flint  and  No.  6  yellow  dent 
(Tables  12  and  12a)  showed  in  all  cases  complete  dominance 
of  yellow.  In  the  Fi  seeds  which  were  of  course  flinty  like  the 
mother,  there  was  no  soft  starch  in  the  cap  and  the  heterozygotes 
were  exactly  like  pure  yellow  flint  seeds.  In  the  Fi  plants  the 
F2  homogygous  and  heterozygous  yellow  seeds  were  also  indis- 
tinguishable. It  was  necessary  to  grow  them  to  distinguish 
heterozygous  yellow  from  homozygous  yellow.  In  the  F2 
plants  with  F3  seeds,  however,  there  was  a  considerable  segre- 
gation of  dented  ears  from  flint  ears.  Here  as  in  the  cross  of 
(1x7)  it  was  fairly  easy  to  distinguish  heterozygous  yellows 
from  homozygous  yellows  when  the  seeds  of  the  former  had  a 
well  developed  soft  starchy  zone  in  the  cap. 

Although  as  has  been  stated  the  Fi  seeds  were  all  exactly 


INHERITANCE   OF   YELLOW   ENDOSPERM. 


49 


like  pure  yellow  flint  seeds,  they  nevertheless  belonged  to  two 
classes.  The  Xenia  seeds  (Fi  seeds)  of  the  hybrid  ear  con- 
tained 159  seeds  which  were  dark  yellow  and  145  seeds  which 
were  a  considerably  lighter  yellow.  This  striking  phenomenon 
was  not  understood  until  another  generation  was  grown  from 
the  seeds.  Table  12  showing  the  selfed  ears  resulting  from  the 
dark  seeds,  and  Table  12a  showing  the  selfed  ears  resulting 
from  the  light  seeds  make  this  matter  plain.  Excluding  ear 
(5  X  6)-9  from  Table  12  because  it  evidently  came  from  a  pure 
yellow  seed  grown  in  this  family  through  an  error,  and  ear 
(5  X  6)-lla  from  Table  12a  which  evidently  grew  from  a  self- 
pollinated  seed  of  the  mother  No.  5,  it  is  clear  that  the  No.  6 
plant  furnishing  the  pollen  for  the  cross  was  homozygous  for 
one  yellow  and  heterozygous  for  the  other.  The  classification 
into  light  and  dark  yellows  was  somewhat  arbitrary  and  there- 
fore some  ears  in  Table  12  gave  ratios  of  3  :  1  and  some  ears 
in  Table  12a  gave  ratios  of  15  :  1  but  the  fact  that  about  one- 
half  of  the  Fi  seeds  had  a  gametic  formula  of  Yi  yi  Y2  ji  and 


TABLE  12. 

F2    SEEDS    FROM   CROSS    OF    NO.    5    WHITE   FLINT   X    NO.    6   YELLOW   DENT. 

Dark  Yellow  Seeds  Planted. 


Ear  No. 

Y 

y 

Ratio  Approx. 

(5  X  6)-l 

326 

29 

15  :  1 

'  )-2 

316 

27 

15  :  1 

'  )-3 

313 

28 

15  :  1 

'  )-7 

354 

122 

3  :  1 

'  )-8 

331 

109 

3  :  1 

'  )-9 

307 

Pure  yellow 

'  )-10 

475 

25 

15  :  1 

'  )-ll 

298 

113 

3  :  1 

'  )-12 

368 

19 

15  :  1 

'  )-13 

363 

35 

15  :  1 

'  )-14 

489 

29 

15  :  1 

'  )-15 

427 

118 

3  :  1 

one-half  the  formula  Yi  yi,  or  Y2  y2,  is  certain.  Ear  (5  x  6)-7a 
is  the  only  ratio  in  doubt.  It  is  probably  15  :  1  as  the  yellows 
were  very  light  and  difficult  to  classify,  and  some  were  probably 
placed  with  the  non-yellows. 


50 


INHERITANCE  IN  MAIZE. 


TABLE  12A. 

F-i   SEEDS   FROM    SAME    CROSS    AS    SHOWN   IN   TABLE    12. 

Light  Yellow  Seeds  Planted. 


Ear  No. 

Y 

y 

Ratio  Approx. 

(5x6 

)-la 

359 

117 

3  :  1 

(    " 

-2a 

144 

54 

3  :  1 

(    " 

-3a 

173 

63 

3  :  1 

(    " 

-4a 

433 

136 

3  :  1 

(    " 

)-5a 

557 

35 

15  :  1 

(    " 

)-6a 

316 

120 

3  :  1 

(  " 

-7a 

450 

49 

10  :  1 

(    " 

-8a 

229 

86 

3  :  1 

(    " 

-9a 

325 

115 

3  :  1 

(    " 

-10a 

227 

87 

3  :  1 

(    " 

-11a 

434 

Pure  white 

(  " 

-12a 

318 

118 

3  :  1 

(    " 

-13a 

256 

93 

3  :  1 

Tables  13,  13a,  b,  c,  d,  show  results  from  an  opposite  cross. 
No.  11,  yellow  flint  was  the  female  parent  and  No.  8,  white 
dent  was  the  male  parent.  There  was  no  effect  of  Xenia,  as 
the  Fi  hybrid  seeds  were  as  yellow  as  the  pure  No.  11.  Table 
13  shows  the  results  from  the  Fi  hybrid  seeds.  Every  ear 
approximates  a  3  :  1  ratio  except  ears  (11  x  8)-7  and  (11  x  8)-8. 
Ear  (11  X  8)-7  is  shown  afterwards  by  Tables  13b  and  c  to  have 
been  in  reality  a  15  :  1  ratio.     In  other  words  it  was  a  Yx  yi  Y2  yj 


TABLE  13. 

F3   SEEDS   FROM   CROSS    OF    NO.    11,    YELLOW   FLINT   X    NO.    8,    WHITE   DENT 

Yellow  Seeds  Planted. 


Ear  No. 

Y 

y 

Ratio  Approx. 

(Ilx8)-1 

358 

154 

3  :  1 

(  "  )-2 

124 

41 

3 

(  "  )-3 

389 

127 

3 

(  "  )-4 

340 

96 

3 

(  "  )-6 

252 

83 

3 

(  "  )-7 

454 

145* 

3 

(  "  )-8 

204 

70** 

3 

*   **  Proved  to  be  a  mixture  of  Y  y  and  y,  with  preponderance  of  Y  y. 


INHERITANCE  OF   YELLOW  ENDOSPERM. 


51 


ear.  Ear  (11  x  8)-8  probably  was  also  of  the  same  character 
as  about  half  of  the  seeds  classed  as  white  proved  to  be  heterozy- 
gous. Table  13d  shows  only  two  ears  out  of  eight  to  have  been 
other  than  white  but  an  inspection  of  the  open  field  crop  showed 
such  a  large  proportion  of  apparently  heterozygous  ears,  that 
this  ratio  is  probably  not  the  real  one. 

Ear  (11  X  8) -2  proved  to  be  Yi  yi  or  Y2  y2  as  is  shown  in  Table 
13a.  There  is  a  ratio  of  about  2  heterozygous  to  1  homozy- 
gous ears. 


TABLE  13A. 

Fs  SEEDS  OF  EAR  NO.  2  OF  CROSS  SHOWN  IN  TABLE  13. 

Yellow  Seeds  Planted. 


Ear  No. 

Y 

y 

Ratio  Approx. 

(llx8)-2-l 

275 

Pure  yellow 

(     "      )-2-3 

237 

75 

3  :  1 

(     "      )-2-5 

244 

71 

3  :  1 

(     "     )-2-7 

374 

Pure  yellow 

(     «     )-2-8 

344 

113 

3  :  1 

(     "     )-2-9 

280 

Pure  yellow 

(     "     )-2-10 

99 

3i 

3  :  1 

(     "     )-2-ll 

173 

38 

3  :  1 

(     "     )-2-15 

274 

75 

3  :  1 

Ear  (11  X  8)-7  was  evidently  wrongly  classified  as  is  shown  in 
Tables  13b  and  13c.  Ear  (llx8)-7-l  is  probably  a  15  :  1 
ratio.  If  this  is  true  then  there  were  2  ears  with  gametic  formula 
Yi  yi  Y2  ya,  2  ears  with  gametic  formula  Yi  yi  or  Y2  y2,  1  ear 
with  formula  Yi  Yi  Y2  Y,  [Ear  (11  x  8)-7-9],  and  3  ears  with 
formula  yi  y2.  The  apparently  white  seeds  from  this  ear  were 
not  all  non-yellow,  but  partly  pure  and  partly  heterozygous 
light  yellows.  That  is,  they  were  Yi  Yi  or  Y2  Y2  or  Yi  yi  or 
Y2  y2. 


52 


INHERITANCE  IN  MAIZE. 


TABLE  13B. 

F3    SEEDS    OF   EAR   NO.    7    OF   CROSS    SHOWN   IN   TABLE    13. 

Yellow  Seeds  Planted. 


Ear  No. 

Y 

y 

Ratio  Approx. 

(11  x8)-7-l 

207 

25 

8  :  1 

(     "      )-7-4 

253 

68 

3  :  1 

(     "      )-7-6 

193 

73 

3  :  1 

(     "      )-7-8 

163 

79 

3  :  1 

(     "      )-7-9 

456 

Pure  yellow 

(     "      )-7-ll 

108 

35 

3  :  1 

(     «      )-7-14 

88 

5 

15  :  1 

TABLE  13C. 

F3  SEEDS  OF  EAR  NO.  7  OF  CROSS  SHOWN  IN  TABLE  13. 

Apparently  White  Seeds  Planted. 


Ear  No. 

Y 

y 

Ratio  Approx. 

(11  x8)-7-la 
(     "      )-7-2a 
(     "     )-7-3a 
(     "      )-7-4a 
(     «      )-7-5a 

271 
323 

504 

330 
117 
300 

Pure  non-yellow 
Pure  light  yellow 
Pure  non-yellow 

3  :  1 
Pure  non-yellow 

TABLE  13D. 

F3  SEEDS  OF  EAR  NO.  8  OF  CROSS  SHOWN  IN  TABLE  13. 

White  Seeds  Planted. 


Ear  No. 

Y 

y 

Ratio  Approx. 

(11  x8)-8-l 

406 

194 

3  :  1 

(     "     )-8-3 

394 

Pure  non-yellow 

(     "     )-8-6 

560 

(     "     )-8-7 

348 

(( 

(     "     )-8-9 

490 

it 

(     "     )-8-ll 

360 

u 

(     "     )-8-12 

360 

u 

(     "     )-8-13 

442 

Pure  yellow 

INHERITANCE   OF   YELLOW   ENDOSPERM. 


53 


TABLE  14. 

f2  seeds  from  cross  of  no.  11  sturges'  yellow  flint  x  no.  24 
sanford's  white  flint. 

Yellow  Seeds  Planted. 


Ear  No. 

Y 

y 

Ratio  Approx. 

(11  X  24)-3 
(   "   )-4 

(   "   )-5 
(  ■  "   )-6 

467 
320 
499 
356 

164 
137 
142 
116 

3  :  1 
3  :  1 
3  :  1 
3  :  1 

Table  14  shows  the  results  from  selfing  the  Fi  seeds  of  a  cross 
between  No.  11,  yellow  flint  and  No.  24  white  flint.  There 
was  no  effect  of  Xenia.  The  ears  gave  3  :  1  ratios  and  the 
extracted  non-yellows  proved  to  be  pure  in  the  Fa  generation. 


TABLE  15. 

F2    SEEDS   FROM   CROSS    OF    NO.    15   LONGFELLOW   FLINT   X    NO.    8 
WHITE   DENT. 

Yellow  Seeds  Planted. 


Ear  No. 

Y 

y 

Ratio  Approx. 

(15x8)-l 

305 

73 

3  :  1 

(  "   )-2 

166 

12 

15  :  1 

(  "   )-3 

246 

85 

3  :  1 

(  "   )-4 

428 

142 

3  :  1 

(  "  )-5 

393 

124 

3  :  1 

(  "  )-6 

353 

106 

3  :  1 

(  "   )-7 

480 

140 

3  :  1 

Table  15  gives  the  results  from  selfing  the  Fi  seeds  of  a  cross 
between  No.  15,  Longfellow  yellow  flint  and  No.  8,  white  dent. 
There  was  no  appearance  of  Xenia  in  the  Fi  seeds.  The  Fj 
seeds  segregated  in  3  :  1  ratios  with  the  exception  of  ear  (15x8)- 
2.  This  ear  was  originally  classified  as  bearing  128  yellow  and 
50  non-yellow  seeds.  The  Fs  seeds  produced  by  the  supposed 
whites,  however,  showed  the  correct  ratio  to  have  been  166 
yellow  and  12  non-yellow.  The  whites  proved  true  in  three 
other   ears.     The   white   seeds   from   ear    (15  x  8)-l    were   not 


54 


INHERITANCE  IN  MAIZE. 


grown,  and  therefore  the  large  excess  of  yellow  seeds  cannot  be 
explained.  It  is  possible  of  course  that  this  ear  as  well  as  one 
or  two  others  that  were  not  planted  really  had  light  yellows 
classified  as  whites.  If  this  were  true  one  might  consider  that 
the  original  mother  plant  was  homozygous  for  one  yellow  and 
heterozygous  for  the  second.  It  seems  not  improbable  that 
this  was  the  case,  for  the  same  results  were  obtained  in  two 
other  instances. 

•  TABLE  16. 

F2   SEEDS   FROM   CROSS   OF    NO.    19    WHITE    SWEET   X    NO.    7 
YELLOW   DENT. 

Yellow  Seeds  Planted. 


Ear  No. 

Y 

y 

Ratio  Approx. 

(19  X  7)-2 
(  "  )-5 

277 
599 

77 
43 

3  :  1 
15  :  1 

One  other  cross.  No.  19  non-yellow  sweet  and  No.  7  yellow 
dent  (Table  16),  gave  di-hybrid  ratios.  The  hybrid  seeds  were 
yellow  starchy  varying  somewhat  in  shade.  Only  two  selfed 
ears  were  obtained  from  the  Fi  seeds.  As  shown  in  Table  16 
one  is  a  3  :  1  ratio  and  one  is  a  15  :  1  ratio.  Here  again  is 
evidence  that  the  male  parent  was  homozygous  for  one  yellow 
and  heterozygous  for  the  second  yellow.  To  be  sure  there  is  a 
slight  excess  of  non-yellows  in  ear  (19  x  7)-5,  but  this  is  accounted 
for  in  the  F3  generation.  The  supposed  non-yellows  gave  one 
heterozygous  yellow  to  seventeen  non-yellows.     The  true  ratio 


TABLE  16A. 

Fj  SEEDS  OF  EAR  5  OF  CROSS  SHOWN  IN  TABLE  16. 

Dark  Yellow  Starchy  Seeds  Planted. 


Ear  No. 

Y 

y 

Ratio  Approx. 

(19  X  7)-5-l 
(  "  )-5-6 
(  "  )-5-9 
(  «  )-5-12 
(  «  )-5-13 

315 
320 
19 
203 
440 

98 
97 
1 
14 
25 

3  :  1 
3  :  1 

15  :  1 
15  :  1 
15  :  1 

INHERITANCE   OF   YELLOW   ENDOSPERM.  55 

then  is  601  :  41  which  is  very  close  to  theoretical  expectancy. 
The  results  from  planting  the  yellow  starchy  seeds  of  (19  x  7)-5 
are  shown  in  Table  16a.  Unfortunately  the  admixture  of 
segregates  with  wrinkled  endosperm  made  these  a  little  difficult 
to  classify,  but  there  is  scarcely  a  doubt  that  2  ears  were  mono- 
hybrids  and  three  ears  di-hybrids,  although  no  dependence 
can  be  placed  on  ear  (19  x  7)-5-9  with  only  20  seeds.  No  pure 
yellows  were  obtained  from  these  seeds  unless  ear  (19  x  7)-5-9 
were  of  this  class.  The  deficiency  of  these  data  was  supplied 
by  the  crop  of  the  yellow  sweet  F2  seeds  of  the  same  ear. 
Twelve  selfed  ears  were  obtained.  They  are  not  given  in  a 
table  because  we  were  not  able  to  prove  the  classification  by 
growing  for  another  generation,  and  it  is  difficult  to  make 
exact  visible  classifications  of  yellow  and  non-yellow  sugar 
seeds.  There  is  scarcely  any  doubt  however  that  two  ears 
were  pure  for  both  yellows  (seeds  all  dark  yellow),  two  pure 
for  light  yellow,  (seeds  all  light  yellow)  three  heterozygous  for 
one  yellow  (seeds  light  yellow  and  white),  one  at  least  and 
probably  two  heterozygous  for  two  yellows  (seeds  dark  yellow, 
light  yellow  and  white)  and  the  rest  homozyous  for  one  yellow 
and  heterozygous  for  one  yellow  (seeds  dark  yellow  and  light 
yellow) . 

This  family  gave  b  y  far  the  best  demonstration  of  two  yellows 
as  far  as  the  eye  is  concerned.  The  ears  homozygous  for  two 
yellows  would  never  have  been  classed  as  the  same  variety  with 
those  homozygous  for  one  yellow.  Nearly  all  the  seeds  were 
absolutely  distinct,  and  yet  when  they  were  arranged  in  a  series 
there  woidd  always  be  a  number  that  were  difficult  to  place. 

Table  17  gives  the  F2  segregates  of  a  mono-hybrid  cross  be- 
tween No.  10  white  flour  and  No.  6  yellow  dent.  There  seems 
to  be  no  question  of  a  di-hybrid  ratio,  but  the  cross  is  interest- 
ing for  another  reason.  The  heterozygous  seeds  are  lighter 
than  the  homozygous  so  that  the  effect  of  Xenia  is  shown 
either  way  the  cross  is  made;  that  is,  Xenia  is  shown  both 
where  white  flour  is  crossed  with  yellow,  and  where  yellow 
Hour  is  crossed  with  white.  The  effect  is  the  same  as  that 
shown  when  light  starchy  caps  are  formed  when  a  starchy 
yellow  dent  is  pollinated  by  a  non-yellow,  but  as  in  this  case 
the  whole  seed  is  floury,  therefore  it  is  all  changed  to  lighter 
yellow. 


56 


INHERITANCE  IN  MAIZE. 


It  might  be  mentioned  that  No.  60  yellow  pop  crossed  with 
No.  2  white,  and  No.  9  yellow  dent  crossed  with  No.  10  flour 
also  show  Xenia.  The  hybrid  seeds  become  so  much  whiter 
that  there  is  no  difficulty  in  distinguishing  the  greater  part  of 
them  from  homozygous  yellows. 


TABLE  17. 

F2    SEEDS    FROM   CROSS   OF   NO.    10    WHITE    FLOUR   AND    NO.    6 
YELLOW   DENT. 

Yellow  Seeds  Planted. 


Ear  No. 

Dark  Y 

Light  Y 

Total  Y 

y 

Ratio  Approx. 

(10x6)-l 

(   "   )-2 
(  "  )-3 
(  "  )-4 

162 
141 
175 
131 

357 
242 
301 
243 

519 
383 
476 
374 

187 
119 
156 
127 

3  :  1 
3  :  1 
3  :  1 
3  :  1 

Conclusions. 

This  completes  the  list  of  crosses  in  which  new  facts  have 
been  observed  in  regard  to  yellow  endosperm.  Other  crosses 
might  be  described  where  simple  mono-hybrid  ratios  were 
obtained,  but  these  have  already  been  described  by  Lock.  The 
di-hybrid  ratios  have  been  described  in  greater  detail  because 
they  belong  to  a  class  of  facts  having  a  very  important  theo- 
retical bearing  on  the  Mendelian  hypothesis,  which  is  discussed 
later  in  the  paper. 

It  should  perhaps  be  stated  that  Correns'  other  general  facts 
have  been  corroborated.  The  pure  extracted  dominants  of 
the  Fs  generation  have  appeared  in  about  the  general  ratio  of 
1  homozygote  to  2  heterozygotes  when  dealing  with  mono- 
hybrids.  There  have  been  insufficient  numbers  to  determine 
the  exact  ratio  of  extracted  dominants  when  dealing  with 
di-hybrids,  but  in  both  cases  the  F4  generations  have  in  every 
case  bred  true.  This  fact  we  hold  to  be  more  important  than 
the  ratio.  It  may  look  somewhat  queer  to  say  that  the  extracted 
F2  non-yellows  have  always  bred  true,  when  a  number  of  cases 
have  been  described  in  which  the  seeds  that  were  thought  to 
be    non-yellows,    proved    to    be    heterozygous    yellows.     This 


PLATE     V. 


At  left,  No.  24  Rhode  Island  white  cap  (white  endosperm),  at  right. 
No.  15  Longfellow  (j-ellow  endosperm).  In  center,  hybrid  showing 
dominance    of    vellow.     Below.    F2    seeds    showing   segregation. 


b.  An  ear  showing  dominance  of  red  pericarp  in  F^.  The  pericarp  has  been 
removed  from  two  rows  of  seeds,  showing  mono-hybrid  segrega- 
tion of  F2  endosperms  beneath  it  into  yellow  and  non-yellow. 


Segregation  of  Yellow   and  Non-Yellow   Endosperm. 


PLATE    VI. 


Cross   24x54.     T.  Ear    ( 24x54 ) -12-5 :    a   ])uvv   extracted   purple.  2.  Ear 

(24x54)-i2-6 ;  purples     208,     non-purples     65,     a    3:1    ratio.  3.  Ear 

(24x5b)-i2-4;  purples    147,    non-purples     117,    a   9:7    ratio.  4.  Ear 

(24x54)-i2-3 ;  a   pure    extracted    non-purple. 


b.  Purple  seeds  produced  by  random  crossing  of  non-purple  seeds  of  ear 
(24x54)-i2  shown  in  Table  i8g.  i.  Ear  (24x54) -12-9x12x8;  ratio 
I  purple:  3  non-purple.  2.  Ear  (24x54)  12-11x12x10;  ratio  i  pur- 
ple :    I   non-purple. 

Inheritance  of  Aleurone  Color. 


INHERITANCE  OF  ALEURONE  COLOR.  57 

is  due  to  the  simple  fact  that  the  seeds  with  the  gametic  formula 
Yi  yi  or  Y2  72  vary  in  color  intensity  so  that  it  is  generally 
impossible  to  classify  correctly  from  1  to  5  seeds  per  ear.  These 
Fo  seeds  prove  their  gametic  structure  in  the  F3  generation; 
and  those  that  have  behaved  as  pure  extracted  non-yellows 
in  F3  have  never  given  anything  but  pure  non-yellows  in  the 
F4  generation. 

The  occurrence  of  the  two  yellow  colors  casts  a  further  doubt 
upon  the  correctness  of  Lock's  work  since  his  main  object  was 
to  show  the  truth  of  Mendel's  mathematical  conclusions  when 
dealing  with  large  numbers.  Our  results  both  here  and  in  the 
case  of  the  purple  aleurone  cells  show  the  futility  of  not  making 
crosses  between  individuals  and  of  not  selfing  individual  Fi 
plants.  This  is  a  further  excuse  for  presenting  in  detail  the 
individual  crosses  between  starchy  and  non-starchy  races  with 
the  same  object  as  Lock. 

Purple  and   Non-purple  aleurone  cells. 

The  consideration  of  the  inheritance  of  this  character  includes 
also  that  of  a  hypostatic  red  color  which  appears  in  crosses 
between  the  various  purple  and  non-purple  families.  The 
pigments  are  both  fairly  easily  soluble  in  water.  They  are 
seen  first  in  the  aleurone  cells  of  the  maturing  seeds  a  few  days 
after  fertilization.  When  the  seed  is  mature  the  red  color 
becomes  an  intense  dark  rose  madder,  and  the  purple  becomes 
almost  black.  Several  tests  of  each  pigment  were  made  by 
macerating  the  aleurone  cells  in  50%  alcohol  and  testing  the 
filtrate.  With  lead  subacetate  both  turned  green  and  a  green 
precipitate  separated.  The  precipitate  from  the  red  seeds  was 
somewhat  darker  and  turned  greenish  brown  on  evaporation 
while  that  from  the  purple  seeds  remained  a  lighter  green. 
Ferrous  sulphate  added  to  the  red  pigment  produced  but  little 
if  any  change  in  color  although  a  dirty  precipitate  separated  on 
shaking.  When  added  to  the  blue  pigment,  however,  a  dark  blue 
precipitate  separated  leaving  the  liquid  colorless.  This  pre- 
cipitate left  a  blue  residue  on  evaporation,  while  the  residue 
from  the  red  pigment  was  simply  a  slight  discoloration,  dark, 
but  with  no  distinct  color  except  possibly  a  redness  at  the 
edges.  Ferric  chloride  however  gave  markedly  different 
reactions  in  the  two  cases.     Added  to  the  red  pigment  an  orange 


58  INHERITANCE  IN  MAIZE. 

color  was  produced  which  became  somewhat  darker  on  evapora- 
tion. The  precipitation  was  sHght.  Added  to  the  blue  pigment 
the  color  was  first  greenish  with  blue  edges.  This  turned  dark 
blue  and  a  bluish  precipitate  separated  which  later  turned 
green  and  remained  so  on  evaporation.  With  ferric  alum  there 
was  no  change  except  that  each  pigment  became  more  intense 
in  color.  Sodium  hydroxide  formed  brownish  green  precipi- 
tates, darker  with  the  purple.  Acids  gave  red  colorations 
which  were  lighter  with  the  red  pigment.  The  acid  and  alkali 
tests  are  evidently  the  usual  reactions  with  vegetable  color 
"indicators"  and  differ  only  through  the  various  amounts  of 
pigment  present. 

It  is  recognized  that  tests  such  as  these  are  arbitrary  in 
nature  and  cannot  form  the  basis  of  conclusions  as  to  the  chemi- 
cal composition  of  the  pigments.  It  seems  certain  however 
that  they  differ  somewhat  in  composition,  although  they  are 
probably  different  stagfes  of  oxidation  of  the  same  color  base. 

It  will  be  seen  in  the  following  pages  that  purple  crossed  with 
different  strains  of  non-purple  gave  different  results.  This 
is  clearly  due  to  the  various  gametic  formulse  possessed  by  the 
different  whites.  It  may  also  be  that  the  purples  differ  some- 
what among  themselves  in  unseen  characters  even  though 
they  were  pure  for  purple  when  selfed.  Our  analysis  of  the 
large  amount  of  data  which  follows  shows  that  there  is  simple 
Mendelian  segregation  and  recombination  of  several  factors 
and  that  there  is  really  no  confusion  of  results  such  as  led 
Correns  and  Lock  to  advance  various  supplementary  hypotheses 
to  account  for  the  facts.  The  use  of  the  color  factor  C,  shows 
how  Lock  obtained  his  purples  by  crossing  white  seeds  sup- 
posedly heterozygous  for  purple,  with  white;  but  it  is  impos- 
sible to  analyze  his  data  since  individual  pollinations  were  not 
made.  A  supplementary  hypothesis  of  Correns  should  also' 
be  mentioned  because,  if  it  were  true  it  would  necessitate  a 
very  different  conception  of  the  interpretation  of  the  inheritance 
of  all  endosperm  characters.  Correns  supposed  that  purple 
X  non-purple  always  gave  purple  while  non-purple  X  purple 
sometimes  gave  non-purple  and  sometimes  gave  purple.  He 
accounted  for  this  by  the  supposition  that  since  the  endosperm 
nucleus  is  formed  by  the  union  of  two  maternal  nuclei  with  one 
paternal  nucleus,  therefore  the  maternal  endosperm  characters 


INHERITANCE  OF  ALEURONE  COLOR.  59 

would  often  dominate  the  paternal  characters  through  the 
effect  of  the  greater  amount  of  maternal  nuclear  material. 
This  is  never  the  case  and  the  fact  is  quite  important.  If  Cor- 
rens'  supposition  were  true  and  the  amount  of  nuclear  matter 
determined  the  characters  to  be  formed,  no  Mendelian  segre- 
gation of  endosperm  characters  and  their  recombination  by 
chance  matings  could  be  demonstrated.  Since  all  of  our  data 
shows  it  to  be  untrue,  it  follows  that  the  quality  and  not  the 
quantity  of  nuclear  material  is  the  important  thing.  The 
nucleus  evidently  regenerates  or  throws  off  material  to  come 
to  its  proper  adjustment  for  the  performance  of  its  functions, 
and  always  in  accordance  with  the  quality  of  its  structure. 

In  order  to  facilitate  a  consideration  of  the  data,  it  will  be 
presented  in  families.  Each  family  comprises  the  progeny 
resulting  from  a  particular  cross.  They  are  taken  up  in  the 
order  of  increasing  complexity. 

Family  (24  and  54) 

This  family  includes  all  of  the  progeny  of  the  cross  of  No.  24 
white  flint  with  No.  54  Black  Mexican  sweet,  this  being  the 
variety  with  purple  aleurone  cells.  The  Black  Mexican  which 
furnished  the  pollen  for  this  cross  had  proved  true  to  the  purple 
color  for  three  generations,  but  pollen  for  the  crosses  of  the 
different  hybrid  families  came  from  several  different  ears.  For 
this  reason  there  is  no  certainty  that  the  purple  aleurone  parent 
had  the  same  gametic  structure  in  each  family.  The  data  for 
the  above  family  are  reported  in  the  sub-divisions  of  Tables 
18  to  20.  In  these  tables  there  is  no  correlation  of  the  purple 
and  starchy  characters,  there  being  a  simple  3  :  1  relationship 
of  starchy  and  non-starchy  seeds  in  both  the  case  where  purples 
and  non-purples  were  obtained  in  F2  in  the  ratio  of  3  :  1  and 
where  they  are  obtained  in  the  ratio  of  9  :  7.  We  may  therefore 
leave  this  character  out  of  consideration  and  consider  only  the 
purple  character. 

The  Fi  seeds  formed  in  the  hybrid  ear  were  all  purple.  Upon 
growing  these  seeds  nine  selfed  ears  were  obtained  with  the 
ratios  of  purples  to  non-purples  shown  in  Table  18.  The  purple 
color  of  these  segregates  was  of  full  depth  and  covered  the 
entire  seed  with  one  or  two  exceptions.  These  exceptions 
were  zygotic  variations  due  to  heterozygosis  and  were  quite 


6o  INHERITANCE  IN  MAIZE. 

different  from  the  partial  or  light  purples  obtained  in  other 
families.  In  the  latter  case  it  was  due  to  a  transmissible  gametic 
factor  which  will  be  explained  later.  Table  18  shows  the 
ratio  of  purples  to  non-purples  to  be  3  :  1  in  the  case  of  seven 
ears  and  9  : 7  approximately  in  the  case  of  two  ears.  This 
immediately  suggests  the  mono-hybrid  ratio  in  the  first  case 
and  a  di-hybrid  ratio  in  the  second  case.  That  this  is  the  true 
state  of  affairs  is  shown  by  the  behavior  of  the  seeds  of  these 
ears  in  later  generations.  The  progeny  of  the  purple  seeds  of 
ear  (24  x  54)-l  (Table  18a)  were  either  pure  purples  or  heter- 
ozygous purples  segregating  in  the  ratio  of  3:1.  The  non- 
purple  seeds  of  the  same  ear  (Table  18b)  produced  only  non- 
purples.  The  same  ratio  was  obtained  from  purple  seeds  of 
ear  No.  (24  x  54)-ll  shown  in  Table  18c. 

The  fact  that  Fs  extracted  non-purple  seeds  continued  to 
breed  true  is  shown  by  the  results  of  the  F4  generation  shown 
in  Table  18d.  Extracted  purple  starchy  seeds  were  also  planted 
from  Ear  No.  (24  x  54)-l-4  and  ten  selfed  ears  proved  pure. 
Twenty-six  ears  were  also  obtained  from  the  open  field  crop 
which  were  also  pure  purple,  six  being  pure  starchy  and  twenty 
heterozygous  starchy. 

These  continued  3  :  1  ratios  with  purity  of  the  extracted 
homozygote  are  what  should  be  expected  from  the  progeny  of 
the  mono-hybrid  ears  of  Table  18.  If  the  9  :  7  ratios  given  by 
ears  No.  9  and  No.  12  of  Table  18  are  true  di-hybrid  ratios 
resulting  from  the  interaction  of  two  factors  both  of  which  are 
necessary  for  the  production  of  the  purple  color,  one  should 
expect  in  the  Fs  generation  but  one  pure  purple  out  of  nine 
to  occur  and  the  remaining  ears  to  be  about  50%  monohybrids 
with  a  3  :  1  ratio  and  50%  di-hybrids  with  a  9  :  7  ratio.  The 
progeny  of  ear  No.  (24  x  54)-12  (Tables  18e,  18f)  shows  how 
nearly  these  expectations  are  confirmed.  Out  of  a  total  of 
nineteen  selfed  ears  two  were  pure  purple,  ten  were  mono- 
hybrids  and  seven  were  di-hybrids.  It  must  be  concluded 
therefore  that  the  purple  color  is  due  to  the  action  of  the  factor 
P  upon  another  color  factor  C,  which  is  probably  similar  in 
nature  to  that  which  Bateson  found  in  sweet  peas.  The  gametic 
structure  of  No.  24,  the  non-purple  variety,  evidently  differed 
in  the  ovules  of  the  seeds  of  the  original  hybrid  ear.  Part  of 
them  lacked  both  P  and  C  and  gave  a  9  :  7  ratio  when  crossed 


INHERITANCE  OF  ALEURONE  COLOR.  6i 

with  the  purple  (C  P),  and  part  of  them  contained  either  P  or 
C  and  therefore  gave  a  mono-hybrid  ratio  when  crossed  with 
C  P.  If  one  supposes  C  to  be  contained  by  the  non-purple 
in  the  first  case  then  the  result  is  as  follows,  Cp  xCP  =  CCPp. 
The  gametes  formed  differ  only  in  presence  or  absence  of  P  and 
a  simple  mono-hybrid  ratio  is  obtained  in  the  F2  generation. 
In  the  second  case  the  cross  is  cpxCP  =  CcPp,  and  the 
F2  populations  have  the  formulae  and  ratios  9CP:3C:3P:1 
c  p,  the  first  nine  being  purple  and  the  last  seven  being  white. 
This  being  the  case  the  various  non-purple  seeds  of  F2  should 
prove  true  non-purples  when  selfed  but  should  sometimes 
give  purples  when  crossed.  The  non-purples  exist  in  the 
following  ratios: 


1 

C 

C 

p 

p 

2 

C 

c 

p 

p 

1 

c 

c 

p 

p 

2 

c 

c 

p 

p 

1 

c 

c 

p 

p 

When  crossed  at  random  there  are  7  x  6  =  42  possible  combi- 
nations of  which  24  should  give  all  non-purple  and  18  some 
purples.  Of  these  eighteen  ears  2  should  be  pure  purples,  8 
purples  and  non-purples  in  the  ratio  1:1,  and  8  purples  and 
non-purples  in  the  ratio  of  1  :  3.  In  Tables  18g  and  18h  besides 
the  selfed  non-purples  seven  combinations  of  different  non- 
purples  are  shown,  besides  several  reciprocal  crosses.  Of  these 
one  combination  and  its  reciprocal  gives  a  1  :  1  ratio  and  one 
combination  and  its  reciprocal  gives  a  1  :  3  ratio. 

None  of  the  F2  seeds  of  the  selfed  ears  of  this  cross  showed  any 
seeds  with  red  aleurone  cells.  Among  the  open  field  ears 
containing  F-.  seeds  however,  were  noticed  several  seeds  with 
aleurone  cells  of  a  peculiar  blue  color  and  several  of  the  red 
color.  Five  selfed  ears  were  obtained  from  the  blue  aleurone 
seeds  (Table  19).  Four  of  these  ears  gave  9  colored  (P  and  R) 
seeds  to  7  non-colored  and  one  gave  a  simple  mono-hybrid 
ratio  in  which  no  reds  were  found.  The  red  seeds  varied  in 
shade  until  the  darkest  seemed  to  the  eye  to  be  purple.  They 
could  be  separated  accurately  only  by  a  microscopic  examina- 
tion of  sections  of  the  aleurone  cells.  The  purples  (the  blue 
seeds  proved  to  be  exactly  like  ordinary  purple  seeds)  occurred 


62  INHERITANCE  IN  MAIZE. 

in  greater  numbers  than  the  reds  but  the  exact  ratios  were  not 
determined  in  this  family,  because  their  parentage  was  not 
certain. 

The  red  seeds  found  in  the  open  field  ears  also  proved  to  be 
heterozygous  for  red  as  shown  by  Table  20.  They  gave  simple 
3  :  1  ratios  except  ear  No.  1  which  proved  to  be  pure  red  although 
heterozygous  for  starchiness.  Fa  seeds  were  obtained  from 
the  red  seeds  of  ear  No.  8  as  is  shown  in  Tables  20a  and  20b. 
It  happened  that  in  this  small  number  five  pure  red  ears  were 
obtained  and  only  three  ears  that  were  heterozygous  and  seg- 
regated in  the  ratio  of  3  :  1. 

Besides  the  ears  shown  in  Table  20a,  two  ears  from  extracted 
red  seeds  were  crossed  with  pure  extracted  non-purples  (whites) 
of  the  Fs  generation  of  cross  (24x54).  Ear  No.  1  gave  125 
purples  and  123  non-purples.  Ear  No.  2  gave  108  purples 
and  124  non-purples.  The  red  ears,  the  maternal  parents  of 
the  crosses,  were  evidently  heterozygous  and  therefore  a  1  :  1 
ratio  was  obtained.  The  non-purple  which  furnished  the 
pollen  must  have  carried  the  P  factor  which  oxidized  the  seeds 
which  otherwise  would  have  become  red  to  the  purple  color. 
This  fact  proves  the  epistatic  nature  of  P  over  R  and  is  a  further 
proof  of  the  di-hybrid  nature  of  the  purple  color.  Another 
ear  crossed  with  non-purples  of  the  same  family  as  above  gave 
all  purple  seeds.  This  ear  evidently  was  homozygous  for  red 
and  all  of  its  seeds  were  oxidized  to  purple.  Two  other  of  these 
red  ears  were  crossed  with  extracted  purples  of  the  same  cross 
from  which  came  the  extracted  whites  used  above.  The  seeds 
of  the  resulting  ears  were  all  purple.     (See  Plate  8a.) 

Several  red  non-starchy  seeds  from  ear  (24  x  R)-16-8  (Table 
20b)  were  also  planted.  Three  selfed  ears  resulted  in  two  pure 
for  red  and  one  giving  248  reds  to  60  non-reds,  a  3  :  1  ratio. 
One  ear  of  this  lot  was  crossed  with  the  same  extracted  purples 
used  in  crossing  the  starchy^  red  seeds  resulting  in  an  ear  with 
all  purple  seeds.  Another  ear  was  crossed  with  one  of  the 
extracted  non-purples  used  in  crossing  the  red  starchy  seeds 
and  resulted  in  an  ear  with  119  purple  starchy  and  124  non- 
purple  starchy  seeds.  The  results  from  the  non-starchy  seeds 
of  this  family  were  therefore  the  same  as  those  from  the  starchy 
seeds. 

The  non-red  seeds  from  (24  x  R)-16-8  both  starchy  and  non- 


INHERITANCE  OF  ALEURONE  COLOR. 


63 


starchy  bred  true  to  the  non-red  character.  Four  crosses 
between  individual  ears  of  this  lot  were  made  and  the  resulting 
seeds  were  all  non-red.  This  is  the  result  which  should  be 
expected  from  an  ear  giving  a  mono-hybrid  ratio  as  did  ear 
(24  X  R)-8  and  shows  that  the  purples  resulting  from  the  crosses 
between  the  non-purples  coming  from  the  9  :  7  ratios  were  not 
accidental. 

TABLE  18. 

F2   SEEDS   FROM   CROSS   OF   NO.   24   WHITE   FLINT   X   NO.   54   PURPLE 
ALEURONE    NON-STARCHY. 

Purple  Aleurone  Starchy  {PS)  Seeds  Planted. 


Ear  No. 

PS 

Ps 

pS 

ps 

Total  P 

Total  p 

Ratio 
Approx. 

(24 

X  54)-l 

207 

67 

67 

27 

274 

94 

3  :  1 

"   )-2 

170 

54 

49 

19 

224 

68 

3 

"   )-6 

197 

65 

59 

24 

262 

83 

3 

( 

"   )-9 

83 

44 

72 

25 

127 

97 

9 

( 

"   )-10 

166 

40 

46 

19 

206 

65 

3 

( 

"   )-12 

153 

40 

115 

40 

193 

155 

9 

"   )-8 

159 

41 

41 

23 

200 

64 

3 

"   )-ll 

166 

55 

47 

22 

221 

84 

3 

*( 

"   )-13 

205 

81 

59 

25 

286 

84 

3 

*  All  purple  seeds  were  full  dark  purples  except  a  few  splashed  purples 
from  this  ear. 


TABLE  18A. 

Fs  SEEDS  OF  EAR  1  OF  SAME  CROSS  AS  TABLE  18. 

Purple  Aleurone  Starchy  {PS)  Seeds  Planted. 


Ear  No. 

PS 

Ps 

pS 

ps 

Total  P 

Total  p 

Ratio 
Approx. 

(24  X  54)-l-3 

144 

Pure  P 

(   "   )-l-4 

384 

Pure  P 

(   "   )-l-5 

96 

PureP 

(   "   )-l-ll 

320 

Pure  P 

(24  X  54)-l-2 

161 

55 

46 

13 

216 

59 

3  :  1 

(   "   )-l-6 

171 

56 

52 

19 

227 

71 

3  :  1 

(   "   )-l-8 

180 

71 

55 

19 

251 

74 

3  :  1 

(   "   )-l-9 

79 

29 

27 

7 

108 

34 

3  :  1 

(   "   )-l-10 

255 

91 

255 

91 

3  :  1 

(   "   )-l-14 

195 

80 

195 

80 

3  :  1 

Total 

1251 

410 

INHERITANCE  IN  MAIZE. 


TABLE  18B. 

Ft   SEEDS  OF  EAR  1  OF  SAME  CROSS  AS  TABLE  18. 

Non-Purple  Aleurone  Starchy  (ps)  Seeds  Planted. 


Ear  No. 

P 

P 

Ratio  Approx. 

24  X  54)-l-4a 

.      "      )-l-5a 
"      )-l-6a 
"      )-l-7a 
"      )-l-15a 

208 
312 
362 
320 
296 

Pure  white 

a 
u 
U 
u 

TABLE  18C. 

F3  SEEDS  OF  EAR  11  (TABLE  18a)  OF  SAME  CROSS  AS  TABLE  18. 

Purple  Aleurone    Non-Starchy  (Ps)  Seeds  Planted. 


Ear  No. 

Ps 

ps 

Ratio  Approx. 

(24x54)-ll-2 

312 

PureP 

(       "      )-ll-3 

368 

a 

(      "      )-ll-4 

280 

li 

(      "       )-ll-l 

240 

82 

3  :  1 

(      "      )-ll-5 

197 

78 

3  :  1 

(       "      )-ll-6 

205 

52 

3  :  1 

(      "      )-ll-ll 

40 

12 

3  :  1 

Total  Het. 

682 

224 

TABLE  18D. 
r4  SEEDS  OF  EAR  (24  X  54)-l-6  (extracted  PS.  TABLE  18b)  of 

SAME   CROSS   AS   TABLE    18. 

Non-Purple  Starchy  (ps)  Seeds  Planted. 


Ear  No. 

ps 

PS 

(24  X  54)-l-6-l 

All 

(      «      )- 1-6-2 

u 

(      "      )-l-6-5 

u 

(      "      )-l-6-8 

u 

(      "      )-l-6-l    x(24x54)-8-5    RS 

All 

(      "      )- 1-6-6    X  (      "      )-8-8    RS 

a 

(      "      )-l-6-12  X  (      "      )-8-3    RS 

i< 

(      «      )-l-6-9    X  (      "      )-8-10  RS 

a 

(      "      )-l-6-10  X  (      "      )-8-l    RS 

u 

Open-field  crop  all  white. 


PLATE    VII. 


a.     Flint  and  dent  segregates  from  F2  of  cross  8x54.     Flint  character  car- 
ried by  No.  54. 


f      ^ 


r  ' 


Z?.  F3  types  from  cross  8x54.  i.  Pure  extracted  purple  (PPCC).  2.  Pure 
extracted  parti-colored  ((PPcc).  3.  Pure  extracted  non-purple 
(ppCC  or  ppcc). 


Inheritance  of  Aleurone  Color. 


INHERITANCE  OF  ALEURONE  COLOR. 


65 


TABLE  18E. 

F»  SEEDS  OF  EAR  (24  X  54)-12  OF  SAME  CROSS  AS  TABLE  18. 

Purple  Starchy  {PS)  Seeds  Planted. 


Ear  No. 

PS 

P 

SS  or  Ss 

Ratio  Approx. 

(24  X  54)-12-l 

280 

Ss 

Pure 

(      «      )-12-2 

147 

40 

Ss 

3  :  1 

(      «      )-12-3 

190 

60 

Ss 

3  :  1 

(      «      )-12-4 

147 

117 

Ss 

9  :  7 

(      «      )-12-5 

288 

Ss 

Pure 

(      «      )-12-6 

208 

65 

Ss 

3  :  1 

(      "      )-12-7 

188 

115 

Ss 

9  :  7 

(      «      )-12-8 

237 

72 

SS 

3  :  1 

(       "      )-12-8i 

212 

72 

Ss 

3  :  1 

(      «      )-12-9 

159 

120 

SS 

9  :  7 

(      «      )-12-10 

145 

56 

Ss 

3  :  1 

(      "      )-12-ll 

95 

30 

Ss 

3  :  1 

(      «      )_i2-12 

179 

59 

Ss 

3  :  1 

TABLE  18F. 

Fj  SEEDS  OF  EAR  (24  X  54)-12  OF  SAME  CROSS  AS  TABLE  18. 

Purple   Non-Starchy  (Ps)  Seeds  Planted. 


Ear  No. 

P 

P 

Ratio  Approx. 

(24  X  54)-12-la 

(      «      )-12-2a 
(      «      )-12-3a 
(      «      )-12-4a 
(      "      )-12-6a 
(      "      )-12-9a 

160 
186 
137 
97 
109 
123 

53 
64 

115 
65 
80 

120 

3  :  1 
3  :  1 
9:7 

9  :  7 
9  :  7 
9  :  7 

TABLE  18G. 

Fi  SEEDS  OF  EAR  (24  X  54)-12  OF  SAME  CROSS  AS  TABLE  18. 

Non-purple  Starchy  (pS)  Seeds  Planted. 


Ear  No. 

P                  p 

Ratio  Approx. 

(24  X  54; 

-12-3b 

All 

(      "      ^ 

-12-4b 

« 

(      "      " 

-12-6b 

(( 

C       "       ' 

-12-7b 

u 

(       "       ^ 

-12-12b 

a 

(       "       ^ 

-12-2b  X 12-4b 

u 

(       "       ^ 

-12-4b  X 12-2b 

u 

(       "       ' 

-12-5b  X 12-lb 

11 

(       " 

-12-8b  X 12-9b                  ] 

L3                 62 

i  :  3 

(       "       ^ 

-12-9b  X 12-8b                 i 

n               226 

1  :  3 

(       "       ' 

-12-10bxl2-llb 

19                86 

1  :  1 

(       "       ' 

-12-llb  X 12-lOb             < 

)3                 99 

1  :  1 

66 


INHERITANCE  IN  MAIZE. 


TABLE  18H. 

Fj  SEEDS  OF  EAR  (24  X  54)-12  OF  SAME  CROSS  AS  TABLE  18. 

Non-Purple   Non-Starchy  (ps)  Seeds  Planted. 


Ear  No. 

P 

P 

(24  X  54)-12-2c 

All 

(■     «       )-12-3c 

u 

(      "      )-12-5c 

a 

(      «      )-12-9c 

u 

(       "       )-12-10c 

u 

(       "       )-12-12c 

u 

(       "       )-12-13c 

u 

(       "       )-12-lc  X 12-4C 

u 

, 

(       "       )-12-4c  X 12-lc 

u 

(      "      )-12-7c  X 12-3c 

u 

(      "       )-12-3c  X 12-7c 

u 

(      "      )-12-6c  X 12-8c 

a 

(       "      )-12-8c  X 12-6C 

tt 

TABLE  19. 

Fa   SEEDS   FROM   CROSS   BETWEEN    NO.   24,    WHITE   FLINT   AND    NO.    XP 
PURPLE   ALEURONE. 

Purple  Aleurone  Starchy  {PS)  Seeds  Planted. 


Ratio 

Ear  No. 

P  +  R 

P 

Approx. 

Notes 

(24  X  P)-16-2 

287 

192 

9  :  7 

SS:  some  seeds 
red 

(     "      )-16-5 

141 

117 

9  :  7 

ss:  few  P's 
strongly  colored 

(     «      )-16-6 

165 

115 

9  :  7 

ss:  few  P's 
strongly  colored 

(     "      )-16-7 

278 

89 

3  :  1 

_  Ss:  84  P's 
lighter  at  cap 

(     "      )-16-8 

253 

193 

9  :  7 

ss:  69  P's 
lighter  at  cap 

TABLE  20. 

Fj   SEEDS   FROM   CROSS   BETWEEN    NO.    24   WHITE   FLINT   AND    NO.     XR 
RED    ALEURONE. 

Red  Aleurone  Starchy  (RS)  Seeds  Planted. 


Ear  No. 

RS 

Rs 

rS 

rs 

Total  R 

Total  r 

Ratio 
Approx. 

(24  X  R)-16-l 
(      "      )-16-4 
(      "      )-16-6 
(      "      )-16-8 

160 

26 

140 

195 

52 
12 
43 
73 

is 

53 
41 

3 

22 
19 

212 

38 
183 
268 

ie 

75 
60 

Pure  red 
3:  1 
3  :  1 
3  :  1 

INHERITANCE  OF  ALEURONE  COLOR.         ( 
TABLE  20A. 

Fs  SEEDS  OF  EAR  (24  X  R)-16-8  OF  SAME  CROSS  AS  TABLE  20. 

Red  Aleurone  Starchy  {RS)  Seeds  Planted. 


Ear  No. 

R 

r 

Ratio  Approx. 

(24  X  R)-16-8-3 
(      "      )-l 6-8-4 
(      "      )-16-8-5 
(      "      )-16-8-6 

(      "      )-16-8-8 

360 
161 
60 
172 
320 

65 
53 

Pure  red 
3  :  1 

Pure  red 
3  :  1 

Pure  red 

TABLE  20B. 

Fs  SEEDS  OF  EAR  (24  X  R)-16-8  OF  SAME  CROSS  AS  TABLE  20. 

Red  Aleurone   Non-Starchy  (Rs)  Seeds  Planted. 


Ear  No. 

R 

r 

Ratio  Approx. 

(24  X  R)-16-8-la 
(      "      )-16-8-2a 
(      "      )-16-8-3a 

160 

248 
280 

60 

Pure  red 

3  :  1 
Pure  red 

Family  (8  x  54) 

The  Fi  Xenia  seeds  of  the  cross  between  No.  8  non-purple 
dent  starchy  and  No.  54  purple  non-starchy  were  all  purple  in 
color.  Four  selfed  ears  were  obtained  when  these  hybrid  seeds 
were  planted.  The  segregation  of  the  F2  seeds  is  shown  in 
Table  21.  A  new  phenomenon  of  peculiar  interest  appeared 
in  this  family.  A  certain  number  of  seeds  were  solid  dark 
purple,  others  were  splashed  dark  purple,  others  were  a  very 
faint  purple  and  have  been  called  particolored,  while  still 
others  were  without  the  purple  color.  The  splashed  dark 
purples  were  seeds  that  had  a  break  in  the  purple  color ;  that  is 
the  purple  color  was  dark  but  appeared  in  patches.  These 
splashed  purples  are  found  in  all  of  the  purple-non-purple 
crosses  except  the  family  *  just  described.  It  seems  evident 
then  that  they  are  due  to  the  interaction  of  characters  which 


Only  one  or  two  splashed  purples  were  ever  found  in  family  (24  x  54). 


68  INHERITANCE  IN  MAIZE. 

happen  to  be  absent  from  the  (24  x  54)  family ;  but  at  the  same 
time  they  are  zygotic  variations  which  are  not  inherited,  for 
their  progeny  are  exactly  like  the  progeny  of  the  dark  purple 
seeds.  Further,  these  patches  are  not  in  a  regular  pattern 
nor  does  the  selection  of  seeds  of  this  nature  have  the  slightest 
tendency  to  fix  the  phenomenon  as  a  separate  character.  There 
is  reason  for  believing  however  that  no  homozygous  purples 
(C  C  P  P)  are  ever  of  this  nature,  and  that  the  splashing  is 
simply  due  to  incomplete  dominance,  but  caused  by  a  factor 
or  factors  brought  in  by  the  non-purple  parent. 

The  fact  that  particolored  or  very  light  purples  which  trans- 
mitted the  character  also  appeared  in  this  family  made  it  seem 
probable  that  a  new  character  had  appeared,  making  the  family 
a  tri-hybrid.  But  this  is  not  the  simplest  interpretation. 
We  have  seen  in  the  other  family  that  the  behavior  of  purple 
is  best  interpreted  as  the  interaction  of  two  factors  C  and  P. 
In  this  family  the  hypothesis  that  either  Cp  or  cP  seeds  are  not 
pure  whites  but  very  light  purples  is  supported  by  all  of  the  data. 
At  first  sight  it  seems  more  reasonable  that  they  should  have 
the  formula  Cp.  If  in  accordance  with  older  interpretations 
of  color  inheritance,  the  purple  color  is  formed  by  an  enzyme, 
P  acting  upon  a  chromogen  C  it  is  more  reasonable  to  suppose 
that  in  the  presence  of  the  chromogen  an  exceedingly  small 
amount  of  the  enzyme  might  give  rise  to  the  particolored  seeds, 
than  it  is  to  believe  that  the  normal  amount  of  enzyme  would 
form  the  purple  color  with  a  trace  of  chromogen.  The  reason 
for  this  statement  rests  upon  the  well  known  fact  that  enzymes 
are  organic  catalysers  and  can  accelerate  reactions  involving 
quantities  very  disproportionate  to  their  own  amount.  There 
is  an  objection  to  this  interpretation,  however,  for  when  parti- 
colored seeds  are  crossed  with  those  having  red  aleurone  cells 
and  which  therefore  have  the  gametic  formula  R  C,  they  invari- 
ably give  purples.  This  proves  that  the  gametic  formula  of 
the  particolored  seeds  is  c  P  and  they  are  so  designated  in  the 
tables. 

The  suggestive  work  of  Miss  Wheldale  (:  09,  :  09a,  :  10)  in 
correlating  the  results  of  biological  chemistry  with  those  of 
genetics,  has  made  it  very  probable  that  a  basic  chromogen  is 
present  in  all  flowers  which  are  able  to  form  a  sap  color,  and 
that  the  complexities  of  color  inheritance  may  be  referred  to 


PLATE   VIII. 


Pure  purple  aleurone  resulting  from  crossing  pure  extracted  red 
aleurone  with  pure  purple.  2.  Same  result  from  crossing  pure  ex- 
tracted red  aleurone  with  colorless  aleurone.  3.  Seeds  half  purple 
resulting  from  crossing  heterozygous  red  aleurone  with  colorless 
aleurone.     4.  Result   from   selfing  the  male  parent  of  3. 


I.  (24x54)8-3  pure  extracted  red  aleurone.  2.  (24x54) -8-6  heterozy- 
gous red  aleurone.  Cut  does  not  show  color  value  when  compared 
with  Fig  a. 

Inheritance   of   Aleurone    Color. 


INHERITANCE  OF  ALEURONE  COLOR.  69 

the  dual  nature  of  the  oxydases  necessary  for  the  formation 
of  the  color  compounds.  It  is  quite  likely  that  the  color  in  the 
aleurone  cells  of  maize  is  similar  in  nature  to  flower  color ;  and, 
as  we  fully  agree  with  Miss  Whedale's  conclusions,  none  of  our 
factors  C,  R  and  P  are  to  be  regarded  as  chromogens.  The 
argument  above  is  in  agreement  with  this  viewpoint.  If  one 
wishes  to  denote  a  chromogen,  the  addition  of  an  X  to  represent 
it,  common  to  both  families,  makes  no  difference  in  the  inter- 
pretation of  the  results. 

If  we  are  dealing  with  a  di-hybrid  ratio,  one  pure  purple  ear 
out  of  every  nine  should  be  expected  in  the  F2  generation. 
Tables  21a  and  21b  show  that  one  such  ear  was  obtained  out 
of  seventeen  ears.  If  the  total  purple  seeds  and  the  sum  of  the 
particolored  and  white  seeds  is  considered  in  Tables  21,  21a 
and  21b  a  close  approximation  to  a  9  :  7  ratio  is  obtained.  If 
the  particolored  seeds  could  in  every  instance  be  distinguished 
from  whites  the  ratio  of  purples  to  particoloreds  to  whites 
should  be  9  :  3  :  4.  It  will  be  noticed  however  that  in  the  ears 
from  which  this  ratio  should  be  expected  there  is  generally  an 
excess  of  whites.  This  is  explained  by  the  fact  that  parti- 
coloreds especially  when  non-starchy  are  not  always  distin- 
guishable from  whites.  The  last  two  ears  shown  in  Table  21d 
are  in  fact  ears  grown  from  seeds  which  were  originally  classed 
as  whites.  If  this  hypothesis  in  regard  to  the  particolored  is 
true,  one  should  expect  the  purple  F2  seeds  to  give  in  the  F3 
generation,  one  ear  pure  purple,  two  ears  showing  segregates 
of  purple  and  particolored  in  the  ratio  of  3  :  1,  two  ears  showing 
segregates  of  purple  and  non-purple  in  the  ratio  of  3  :  1,  and 
four  ears  showing  purples,  particolored  and  non-purples  in  the 
ratio  9:3:4.  Among  the  ears  received  (Tables  21a,  21b) 
there  were  one  of  the  first  class,  six  of  the  second  class,  three 
of  the  third  class  and  seven  of  the  fourth  class. 

Tables  21c  and  21d  show  the  results  from  growing  the  parti- 
colored seeds  of  the  same  ear.  No.  (8  x  54) -1.  One  ear  should  be 
pure  particolored  to  two  showing  segregates  of  particolored  and 
non-purple  in  the  ratio  of  3  :  1.  Out  of  the  fifteen  ears  obtained 
three  were  evidently  of  the  first  class  and  twelve  of  the  second 
class. 

In  all  of  these  tables  the  progeny  of  hybrid  starchy  seeds 
segregated  normally. 

Seeds  classified  as  non-purples  were  also  planted  from  this 


70  INHERITANCE  IN  MAIZE. 

same  ear  No.  (8  x  54) -1.  The  thirteen  selfed  ears  resulting 
as  progeny  of  starchy  seeds  all  proved  to  be  non-purple.  Two 
particolored  ears,  however,  appeared  in  the  eight  selfed  ears 
resulting  from  planting  non-purple,  non-starchy  seeds.  This 
showed  that  there  was  more  difficulty  in  classifying  the  non- 
starchy  non-purples  than  in  classifying  starchy  non-purples. 
Non-purple  seeds  planted  from  ear  No.  (8  x  54)-5  also  gave  a 
few  particolored  progeny. 

Four  thousand  seeds  from  tested  whites  of  the  Fs  seeds  were 
planted  in  an  isolated  plot  the  next  season  and  were  allowed  to 
inter-cross  naturally.  If  we  were  dealing  with  di-hybrid  non- 
purples  in  this  case,  such  inter-crossing  should  give  some  purples, 
such  as  were  obtained  in  the  (24  x  54)  family.  The  resulting 
crop  of  this  large  number  of  plants  however  were  all  true  non- 
purples,  proving  that  we  were  dealing  with  non-purples  with 
formulas  either  CC,  Cc  or  cc.  Further  proof  of  the  constitution 
of  the  particolored  is  shown  in  the  following  facts.  No  parti- 
coloreds  ever  gave  full  purples.  Furthermore,  pure  extracted 
particoloreds  (c  c  P  P)  from  ear  No.  (8  x  54)-l-13b  of  Table  21c 
were  grown  for  another  generation  and  their  gametic  structure 
tested  by  various  crosses.  Several  of  these  ears  were  selfed  and 
all  proved  to  be  pure  particoloreds  (ccPP).  Three  different 
ears  were  crossed  with  pure  extracted  purples  from  progeny  of 
ear  No.  (24  x  54) -1-4.  As  would  be  expected  all  of  the  seeds 
were  purple.  Two  of  the  ears  however  had  a  decided  reddish 
purple  color  while  one  was  dark  purple  without  the  reddish 
tint.  Four  ears  were  crossed  with  extracted  red  seeds  (RRCC)- 
All  produced  purple  seeds.  Nine  ears  were  crossed  with  plants 
of  the  progeny  of  the  non-purples  of  ear  No.  (24  x  54) -12.  It 
will  be  remembered  that  this  ear  gave  a  ratio  of  nine  purples  to 
seven  non-purples.  The  seven  non-purples  would  have  the 
following  formulse:  1  PPcc,  2  Ppcc,  1  ppCC,  2  ppCc,  Ippcc. 
Crossing  the  particoloreds  at  random  with  pollen  of  individual 
plants  of  this  lot  should  give  on  the  average  one  ear  with  all 
purple  seeds  when  pollinated  by  ppCC,  two  ears  with  50% 
purple  and  50%  particolored  when  pollinated  by  ppCc,  four 
ears  pure  particolored  when  pollinated  by  PPcc,  Ppcc  or  ppcc. 
Nine  ears  were  obtained  of  which  one  had  all  purple  seeds, 
three  had  50%  purple  and  50%  particolored  with  a  total  of 
308  purple  seeds  to  294  particolored  seeds  and  five  were  all 


INHERITANCE  OF  ALEURONE  COLOR. 


n 


particolored.  It  should  be  mentioned,  however,  that  the 
particolored  seeds  obtained  by  crosses  with  the  whites  of  this 
(24  X  54)  family  in  which  the  (ccPP)  seeds  were  not  particolored, 
gave  seeds  which  averaged  much  lighter  in  appearance  than 
the  pure  particolored.  In  other  words  particoloreds  crossed 
with  whites  of  other  families  show  imperfect  dominance  of 
particolored.  Some  gene  common  to  both  parents  of  the 
(8  X  54)  family,  therefore,  accounts  for  the  production  of  the 
color. 

These  two  families  differed  in  no  other  endosperm  character 
except  presence  and  absence  of  starchiness.  No  correlation 
of  any  kind  was  observed  between  these  two  allelomorphic 
pairs. 


TABLE  21*. 

Fj   SEEDS   FROM    CROSS    BETWEEN    NO.    8    NON-PURPLE   DENT   STARCHY 
AND    NO.    54   PURPLE    NON-STARCHY. 

Purple  Seeds  Planted. 


Total 

Total 

Ear  No. 

CP 

cP 

Cp  or  cp 

Purple 

Non-Purple 

(8  X  54)-l 

297 

75 

146 

297 

221 

(     "      )-2 

230 

75 

172 

230 

247 

(     "      )-3 

302 

239 

(     "      )-5 

270 

229 

Total 

1099 

936 

*  There  were  1,514  starchy  and  521  non-starchy  seeds. 


72 


INHERITANCE  IN  MAIZE. 
TABLE  21A*. 

Fa   SEEDS   OF   EAR   NO.    (8  X  54)-l    OF   TABLE   21. 

Purple  Starchy  (PCS)  Seeds  Planted. 


Total 

Total 

Starch- 

Ear  No. 

CP 

cP 

Cp  or  cp 

Purple 

Non-Pur. 

mess 

(8  X  54)-l-l 

233 

70 

233 

70 

SS 

(  "  )-l-2 

16 

6 

7 

16 

13 

Ss 

(  "  )-l-3 

238 

69 

238 

69 

Ss 

(  "  )-l-4 

321 

86 

321 

86 

Ss 

(  "  )-l-6 

312 

Ss 

(  "  )-l-8 

239 

106 

93 

239 

199 

Ss 

(  "  )-l-9 

223 

65 

95 

223 

160 

SS 

(  "   )-l-12 

285 

66 

285 

66 

SS 

(  "  )-l-14 

160 

33 

111 

160 

144 

.  Ss 

(  "  )-l-20 

126 

54 

126 

54 

SS 

*  There  were  1,362  starchy  and  435  non-starchy  seeds  in  the  Ss  ears. 


TABLE  21B. 

F3   SEEDS   OF   EAR   NO.    (8  X  54)-l    OF   TABLE   21. 

Purple   Non-Starchy  (PCs)  Seeds  Planted. 


Ear  No. 

CP 

cP 

Cp  or  cp 

Total 
Purple 

Total 
Non-Purple 

(8  X  54)-l-la 

229 

79 

229 

79 

(  "  )-l-3a 

236 

44 

116 

236 

160 

(  "  )-l-4a 

295 

93 

295 

93 

(  "  )-l-6a 

260 

86 

260 

86 

(  «  )-l-7a 

86 

20 

38 

86 

58 

(  "  )-l-10a 

239 

89 

239 

89 

(  "  )-l-lla 

223 

55 

88 

223 

143 

INHERITANCE  OF  ALEURONE  COLOR. 
TABLE  210*. 

Fj   SEEDS   OF   EAR   NO.    (8  X  54)-l    OF   TABLE   21. 

Particolored  Starchy  (cPS)  Seeds  Planted. 


73 


Ear  No. 

cP 

Cp  or  cp 

Starchiness 

(8  X  54)-l-2b 

322 

99 

SS 

(  "  )-l-5b 

402 

ss 

(  «  )-l-6b 

115 

70 

Ss 

(  «  )-l-7b 

150 

64 

SS 

(  «  )-l-10b 

386 

SS 

(  "  )-l-llb 

254 

92 

Ss 

(  "  )-l-13b 

427 

Ss 

(  "  )-l-14b 

262 

112 

SS 

(  "  )-l-15b 

256 

133 

Ss 

*  There  were  1,026  starchy  and  321  non-starchy  seeds  in  the  Ss  ears. 


TABLE  21D. 

Fs   SEEDS   OF   EAR   NO.    (8  X  54)-l    OF   TABLE   21. 

Particolored   Non-Starchy  (,cPs)  Seeds  Planted. 


Ear  No. 

cP 

Cp  or  cp 

(8  X  54)-l-2c 
(  "  )-l-3c 
(  "  )-l-4c 
(  «  )-l-5c 
(  "  )-l-lw 
(  «  )-l-12w 

149 
364 
168 
123 
230 
131 

110 

'89 
59 

115 
99 

74  INHERITANCE  IN  MAIZE. 

Family  (15  x  54). 

This  family  brings  in  a  third  allelomorphic  pair  namely 
presence  and  absence  of  yellow  in  the  endosperm.  No.  15  is 
Longfellow  pure  for  the  presence  of  starchiness  and  for  a  single 
yellow  factor.  This  cross  was  made  to  find  out  whether  there 
were  further  differences  in  the  behavior  of  the  purple  factor 
when  crossed  with  other  non-purples,  and  it  was  thought  that 
the  yellow  endosperm  might  prove  a  disturbing  factor.  This 
is  not  the  case  for  the  Fi  seeds  were  all  purple  with  the  exception 
that  a  few  splashed  purples,  which  behaved  like  the  normal 
hybrid  purples,  also  occurred  in  this  family.  Eight  ears  were 
obtained  by  growing  the  Fi  seeds,  and  starchiness  and  yellow- 
ness were  found  to  segregate  in  a  normal  manner.  There  was 
a  total  of  1765  Y  to  604  y  and  1746  S  to  623  s  seeds. 

There  is  only  one  fact  of  particular  interest  in  this  family. 
Table  22  shows  the  eight  selfed  Fi  ears  grown  from  the  purple- 
starchy  hybrid  seeds,  containing  the  F2  seeds.  It  will  be 
noticed  that  in  the  table,  six  of  the  ears  appear  to  show  mono- 
hybrid  segregation  and  two  of  them  di-hybrid  segregation. 
This  is  not  really  the  case.  All  of  the  ears  giving  the  3  :  1  ratio 
were  also  di-hybrids.  The  figures  in  the  column  headed  "Purple" 
contained  purples,  splashed  purples  and  particoloreds.  Some 
unknown  cause  produces  many  seeds  in  this  cross  that  are 
heavily  splashed  with  purple.  These  always  behaved  as 
heterozygous  purples,  although  the  heterozygous  purples  were 
not  always  splashed,  but  were  generally  full  colored  purples. 
The  particoloreds  are  seeds  containing  the  P  factor  but  lacking 
the  C  factor  as  in  cross  (8  x  54) .  The  difficulty  here  was  to 
distinguish  by  sight  all  of  the  splashed  purples  (P  C)  from  the 
particoloreds  (Pc).  They  were  all  included  in  the  table  there- 
fore as  "Purples." 

The  ears  (15  x  54) -2  and  (15  x  54) -3  did  not  show  parti- 
colored seeds,  but  that  the  same  gametes  were  concerned  is 
shown  by  the  following  data.  Theoretically,  if  ear  (15  x  54)-2 
is  a  di-hybrid  the  purple  seeds  when  selfed  should  give  1  ear 
with  all  purple  seeds,  4  ears  with  3  purple  seeds  to  1  non- 
purple  seed  and  4  ears  with  9  purple  seeds  to  7  non-purple  seeds. 
Twelve  selfed  ears  were  obtained  in  the  next  generation.  One 
had  all  purple  seeds.     Seven  had  purple  and  non-purple  seeds 


INHERITANCE  OF  ALEURONE  COLOR.  75 

at  the  ratio  of  9  :  7,  there  being  a  total  of  1035  purple  and  763 
non-purple  seeds.  Four  had  purple  and  non-purple  seeds  at 
the  ratio  of  3  :  1,  there  being  a  total  of  480  purple  to  162  non- 
purple  seeds.  It  should  be  remarked  that  in  two  of  these  ears 
a  few  very  light  particolored  seeds  were  found,  showing  that 
the  seemingly  aberrant  ear  (15  x  54) -2  had  a  slight  tendency 
to  throw  particoloreds  like  the  other  ears  of  the  family.  There 
is  also  some  evidence  that  microscopical  examination  of  the 
embryo  stem  would  show  particoloreds  in  the  ordinary  ratio. 

The  non-purples  from  this  ear  were  also  grown.  Eighteen 
selfed  ears  were  obtained.  All  of  them  were  true  to  non-purple. 
Two  of  them  had  a  few  particolored  seeds  (6  in  one  case  and  14  in 
another).  These  seeds  might  possibly  have  been  produced  by 
the  contamination  of  a  few  grains  of  foreign  pollen,  but  they 
might  very  well  be  white  seeds  of  the  formula  Pc  which  were 
showing  the  racial  tendency  to  a  slight  production  of  pigment 
(i.  e.  particoloreds). 

Non-purples  from  the  other  aberrant  ear  No.  (15  x  54) -3  were 
also  grown  and  when  selfed  gave  only  non-purples.  Three  inter- 
crosses and  their  reciprocals  were  made  between  different  plants 
from  this  lot.  It  happened  that  no  purple  seeds  were  obtained 
as  should  be  expected  in  a  portion  of  the  cases,  as  explained 
before.  That  the  non-purples  did  differ  in  composition  among 
themselves  was  shown  however  by  crossing  a  pure  particolored 
(PPcc)  of  the  (8  X  54)  family  with  pollen  from  one  of  our  non- 
purples,  ear  No.  (15  x  54)-3-10.  The  ear  resulting  from  the 
cross  had  179  purple  seeds  and  168  particolored  seeds.  This 
1:1  ratio  could  only  have  been  obtained  from  a  non-purple 
heterozygous  for  C  (Cc).  As  a  non-purple  with  the  formula 
Co  could  only  have  been  obtained  from  a  di-hybrid  cross,  it  is 
proved  that  all  of  the  ears  of  this  family  were  di-hybrids.  The 
complete  gametic  structure  of  the  hybrid  seeds,  speaking  of 
endosperm  characters  only,  is  YySsCcPp. 


76 


INHERITANCE  IN  MAIZE. 


TABLE  22. 

Fi    SEEDS   FROM   CROSS   BETWEEN   NO.   15   NON-PURPLE   YELLOW 
STARCHY   AND   NO.   54   PURPLE   NON-STARCHY. 

Purple  Seeds  Planted. 


Ear  No. 

Purple* 

Non-Purple 

Ratio  Approx, 

(15  X  54)-l 

138 

45 

9-f3  :  3  +  1 

(      "      )-2 

203 

135 

9  :  7 

(      "      )-3 

109 

83 

9  :  7 

(      "      )-4 

250 

84 

9-t-3  :  3-fl 

(       "      )-6 

201 

61 

9-1-3  :  3-hl 

(      "      )-8 

307 

91 

9+3  :  3  +  1 

(      "      )-ll 

254 

93 

9+3  :  3  +  1 

(      "      )-15 

239 

76 

9+3  :  3  +  1 

*  Every  ear  except  ears  2  and  3  contained  splashed  purples  ■which 
act  as  heterozygous  purples  in  inheritance  and  particoloreds  which  act 
as  if  they  had  the  gametic  formula  (cP),  but  the  intergradations  were  so 
gradual  that  it  was  impossible  to  make  an  accurate  classification.  The 
matter  is  not  worth  mentioning  here  except  for  the  reason  that  persons 
who  had  not  had  experience  with  the  behavior  of  purple  and  non-purple 
crosses  in  other  families  would  be  utterly  at  loss  for  a  classification  and 
it  would  be  necessary  for  them  to  grow  each  individual  seed  for  another 
generation  to  determine  its  gametic  formula. 


Family  (18  x  58) 

No.  18,  the  female  parent  of  this  cross  is  a  small  non-purple 
sugar  maize  which  usually  has  twelve  rows.  The  purple  parent 
is  a  small  eight-rowed  flint. P  The  Fi  seeds  were  purple.  Only 
one  selfed  ear  was  obtained  from  the  Fi  plants  through  an 
unfortunate  loss  of  pollen.  The  segregation  of  F2  seeds  is  shown 
in  Table  23.  The  hybrid' 'seeds  have  the  gametic  formula  Pp 
RrCc'.  The  seeds  with  the  formula  PR  and  probably  also 
with  the  formula  P  give  particoloreds  or  very  light  purples  as 
they  did  in  family  8  x  54.  They  were  very  light  however  and 
the  138  seeds  classed  as  whites' or  non-purples  contained  same 
particoloreds  as  is  shown  in  thelFs  generation.  Theoretically 
in  the  F2  generation  there  should  be  36  purples  (27  PRC+9  PC)', 
9  reds  (RC),  12  particoloreds  (9  PR +3  P)  and  7  whites  (3  C+3 


PLATE    IX. 


'-¥f<**i(^ 


a.     F3    color    segregates    from    cross    (18x58).     i.  Pure    extracted   purple. 
2,  3.  Ears  from  heterozygous  plants.     4.   Pure  extracted  hon-purple. 


:  — ^  - 
^T  r 


b.  F3  color  segregates  from  cross  (18x58).  i.  Pure  extracted  red. 
2,  3.  Ears  from  heterozj'gous  plants.  4.  Pure  extracted  non-red. 
Proper  color  values  are  not  shown. 

Inheritance  of  Aleurone  Color. 


INHERITANCE  OF  ALEURONE  COLOR.         n 

R+1  pre).  There  is  an  excess  of  whites  because  the  parti- 
coloreds  could  not  be  classified  easily,  so  it  might  be  said  that 
there  should  be  36  purples:  9  reds:  19  particoloreds  and  whites. 
In  the  one  ear  obtained  there  is  still  an  excess  of  the  last  class, 
but  the  behavior  of  the  seeds  in  the  Fs  generation  proves  the 
gametic  constitution  of  the  parents.  Tables  23a  and  23b  give 
the  results  from  planting  purple  F2  seeds.  The  last  four  ears 
shown  in  Table  23a  were  planted  from  splashed  purples  but 
they  gave  the  same  result  as  the  full  purples.  We  may  con- 
clude therefore  that  splashed  purples  behave  the  same  as  self- 
colored  purples  in  inheritance.  Theoretically  the  entire  lot 
of  purples  should  have  the  following  gametic  constitutions  and 
proportions : 

Class    1.     1  P  P  R  R  C  C  =        Pure  purple. 

"        2.     2PpRRCC=     3  purple:    1  red. 

"        3.     2PPRrCC=        Pure  purple. 

"        4.     2PPRRCc=     3  purple:   1  white. 

"        5.     4  P  p  R  r    C  C  =  12  purple:   3  red:   1  white. 

"        6.     4PpRRCc=     9  purple:     3   red:     4   white.     3 

being  particolored. 

"  7.  4  P  P  R  r  C  c  =  12  purples:  4  white.  3  being  part- 
icolored. 

"        8.     8  P  p  R  r    C  c    =  36  purples:  9  reds:  19  whites.   12 

being  particolored. 

«        9.     1  P  P  C  C  =        Pure  purple. 

"      10.     2  P  p  C  C\  o  1        1     u-^ 

"      11      2PPCcJ  ^        purples:   1  white. 

"      12.     4PpCc  =9  purples:    7  whites  and  parti- 

coloreds. 

These  ears  when  selfed  should  give  the  proportions  shown  at 
the  right  of  the  above  column.  An  examination  of  Tables  23a 
and  23b  show  that  out  of  the  23  selfed  ears  obtained  the  expected 
ratios  were  followed  rather  well.  There  were  two  pure  purple 
ears,  Classes  1,  3  and  9;  2  ears  of  Class  2;  3  ears  of  Class  12;  4 
ears  of  Classes  4,  7,  10  and  11  which  collectively  give  3  purples: 
1  white;  3  ears  of  Class  8;  9  ears  of  Classes  5  and  6.  The  parti- 
colored seeds  are  very  light  in  color  and  although  they  are 
classified  as  nearly  as  possible  in  the  tables  this  classification 
should  be  considered  only  an  approximation  and  not  a  reality. 


78 


INHERITANCE  IN  MAIZE. 


Particoloreds  and  whites  are  considered  together  in  determining 
the  gametic  constitution  of  the  ears.  The  particolored  seeds 
proved  to  be  true  particoloreds  of  the  same  nature  as  those  of 
family  (8  x  54) .  The  selfed  ears  resulting  from  such  seeds  of 
ear  No.  (18  x  58) -1  of  Table  23,  gave  no  purples.  Pure  parti- 
coloreds ears  and  heterozygous  particolored  ears  were  obtained 
but  no  exact  visual  classification  of  the  latter  could  be  made 
and  it  was  not  considered  worth  while  to  determine  their  precise 
constitution  by  breeding. 

The  red  segregates  occurring  in  ear  No.  (18  x  58) -1  were  also 
tested  in  the  F3  generation.  Fifteen  selfed  ears  were  obtained 
and  are  shown  in  Table  23c.  Among  them  were  five  pure  red 
ears,  six  which  threw  reds  and  whites  in  the  ratio  of  9  :  7  and 
four  which  threw  reds  and  whites  in  the  ratio  3:1.  The 
number  of  pure  red  ears  obtained  was  slightly  greater  than 
should  generally  be  expected  but  such  a  deviation  should  occur 
about  once  out  of  five  times  when  dealing  with  lots  of  only 
fifteen  ears.  The  selfed  white  segregates  of  ear  No.  (18  x  58)-l 
of  Table  23  yielded  about  one  particolored  ear  either  homo- 
zygous or  heterozygous  out  of  every  four.  This  shows  the  error 
in  trying  to  classify  particolored  and  white  seeds.  There  is  no 
doubt  however  that  when  pure  white  segregates  are  planted 
they  always  breed  true. 


TABLE  23. 

Fa   SEEDS   OF   CROSS   BETWEEN   NO.    18   NON-PURPLE   NON-STARCHY 
AND   NO.    58   PURPLE   STARCHY. 


Ear  No. 

Purple 
PCR  +  PC 

Red 
RC 

Particolored 
PR-fP 

Non-Purple 
+  some  P 

(18x58)-! 

191 

56 

42 

138 

INHERITANCE  OF  ALEURONE  COLOR. 


79 


TABLE  23A. 

F3   SEEDS   OF   EAR    (18  X  58)-l    OF   TABLE   23. 

Purple  Starchy  Seeds  Planted. 


Ear  No. 

Purple 

Red 

*  Parti- 
colored 

Non-Purple 

(18  X  58)-l-l 

167 

49 

84 

(       "       )-l-2 

18 

4 

(       "       )-l-3 

41 

13 

(      "      )-l-6 

211 

72 

92 

(      "      )-l-8 

221 

66 

96 

(      «      )-l-8a 

138 

65 

83 

(       "       )-l-ll 

80 

(       "       )-l-12 

66 

i7 

i2 

17 

(       "       )-l-ls 

240 

78 

(       "       )-l-2s 

141 

48 

72 

65 

(       "      )-l-3s 

121 

38 

113 

(       «      )-l-4s 

93 

21 

15 

60 

s  Planted  splashed  purples. 

Particolored  classification  is  only  approximate. 


TABLE  23B. 

F3    SEEDS    OF   EAR    (18  X  58)-l    OF   TABLE   23. 

Purple   Non-Starchy  Seeds  Planted. 


Ear  No. 

Purple 

Red 

*  Parti- 
colored 

Non-Purple 

(18  X  5S)-l-2 

49 

25 

26 

(      "      )-l-3 

68 

20 

5 

66 

(      "       )-l-4 

183 

61 

73 

(      "       )-l-5 

240 

61 

(       "       )-l-6 

22 

7 

8 

(      "      )-l-7 

207 

147 

(      "      )-l-8 

184 

24 

140 

(      "      )-l-9 

360 

(      "      )-l-10 

186 

68 

(      "      )-l-ll 

99 

22 

41 

(      "       )-l-12 

84 

34 

*  Particolored  classification  is  only  approximate. 


8o 


INHERITANCE  IN  MAIZE. 


TABLE  23C. 

F,    SEEDS    OF   EAR    (18  X  58)-l    OF   TABLE   23. 

Red  Starchy  Seeds  Planted. 


Ear  No. 

Purple 

Red 

Non-Purple 

Ratio 
Approx. 

(18  X  58)-l-l 

222 

162 

9  :  7 

(      "      )-l-2 

350 

Pure 

(      "      )-l-3 

222 

'so 

3  :  1 

(      "      )-l-5 

212 

171 

9  :  7 

(      "      )-l-6 

195 

115 

9  :  7 

(      "      )-l-7 

148 

74 

3  :  1 

(      "      )-l-12         ! 

187 

102 

9  :  7 

(      «      )-l-2s 

300 

Pure 

(      "      )-l-3s 

350 

Pure 

(      «      )-l-4s 

276 

Pure 

(      "      )-l-6s 

209 

'63 

3  :  1 

(      "      )-l-7s 

44 

35 

9  :  7 

(      "      )-l-9s 

237 

141 

9  :  7 

(      «      )-l-10s 

361 

Pure 

(      "      )-l-lls 

206 

"ei 

3:1 

s  Red  sugar  (s)  seeds  planted. 

Family  (7  x  54) 

This  cross  introduces  a  combination  of  yellow  endosperm 
and  a  dent  character,  the  Learning  parent  having  long  dented 
yellow  seeds  usually  with  formulae  Y1Y1Y2Y2.  The  current 
efifect  of  the  cross  gave  purple  seeds  some  of  which  were  splashed 
as  in  the  previous  case  where  yellow  flint  was  the  non-purple 
parent.  There  was  nothing  of  special  interest  in  the  F2  gene- 
ration as  the  ears  segregated  purple  and  non-purple  seeds  in 
di-hybrid  ratios  without  the  appearance  of  particolored  (cP) 
seeds.  The  characters  in  which  these  parent  varieties  differed 
segregated  absolutely  independently  of  each  other. 

Family  (17  x  54) 

The  yellow  flint  which  is  the  non-purple  parent  in  this  family 
is  similar  to  No.  15.  The  ear  is  shorter,  however,  and  has 
present  a  red  pericarp  color  described  under  pericarp  color  as  R4. 
The  Fi  seeds  were  purple.  They  were  sometimes  splashed 
purples  but  more  rarely  than  in  the  other  crosses.  The  F2  seeds 
gave  a  simple  mono-hybrid  ratio  but  they  were  not  followed 
into  further  generations.  The  plant  of  No.  17  used  as  the 
parent  was  homozygous  therefore  'for  either  C.  or  P. 


PLATE    X. 


No.  54.  Black  Mexican  sugar  and  No.  60  Tom  Thumb  pop  above.  Be- 
low F  J  ears  with  F2  seeds.  At  left  ear  from  the  famity  without 
factor  inhibiting  the  formation  of  color  in  aleurone  cells.  Other 
ears  contain  this  inhibiting  factor   (heterozygous  in  mother  plants). 


Inheritance  of  Aleurone  Color. 


INHERITANCE  OE  ALEURONE  COLOR.  8i 

Family  (19  x  54) 

No.  19  the  female  parent  of  this  cross  is  a  large  sugar  corn 
comparable  in  size  with  the  large  dent  varieties.  The  Fi  seeds 
were  deep  purple  and  the  F2  seeds  segregated  in  ratios  exceed- 
ingly close  to  the  theoretic  number  for  mono-hybrids. 

Family  (60  x  54) 

No.  60  is  a  dwarf  pop  maize  with  a  yellow  endosperm,  known 
as  Tom  Thumb.  The  individuals  used  as  parents  in  the  various 
crosses  were  pure  Tom  Thumbs  but  it  is  not  certain  that  they 
were  the  product  of  a  single  selfed  ear.  They  were  grown  from 
an  ear  which  was  self -pollinated,  but  because  the  silks  appear 
in  this  variety  while  the  young  ear  is  entirely  hidden  in  the 
axil  of  the  leaf,  it  is  less  certain  that  foreign  pollen  was  excluded 
from  the  bagged  ears  than  it  is  in  the  case  of  our  other  crosses. 
The  bags  were  slipped  down  into  the  leaf  axil  as  firmly  as  pos- 
sible but  there  was  still  some  chance  for  cross  pollination. 
This  chance  existed  only  among  plants  of  the  same  variety, 
however,  for  no  other  pollen  was  mature  at  the  same  time. 
As  several  of  these  crosses  were  made  upon  different  plants 
of  variety  No.  60  it  is  not  strange  therefore  that  one  or  two 
of  the  crosses  acted  as  if  parents  with  different  gametic  formulae 
had  been  used.  It  does  not  follow  that  this  was  the  case, 
for  the  Tom  Thumb  or  the  Black  Mexican  or  both  might  have 
been  heterozygous  in  some  non-visible  character. 

The  result  of  the  immediate  cross  was  different  from  our  other 
crosses  in  which  the  purple  aleurone  cells  were  concerned;  some 
of  the  seeds  were  dark  purple,  some  were  varying  shades  of 
light  purple  and  some  were  white  (i.  e.  non-purple).  The 
behavior  of  the  purple  and  non-purple  hybrid  seeds  in  the  next 
generation  showed  conclusively  that  we  were  dealing  neither 
with  a  reversal  of  dominance  nor  with  a  character  in  which  the 
female  gametes  segregated  normally  and  the  male  gametes 
abnormally  as  suggested  by  Correns,  but  with  an  entirely  new 
dominant  factor  in  which  the  Tom  Thumb  variety  was  probably 
heterozygous.  This  factor  we  take  to  be  an  actual  inhibiting 
factor  similar  in  action  to  the  dominant  white  found  in  poultry. 
It  is  also  analogous  to  the  latter  in  that  it  does  not  always 
completely   inhibit   the   development   of   color,   in   which   case 


82  INHERITANCE  IN  MAIZE. 

light  purples  similar  in  appearance  to  the  particoloreds  of 
earlier  crosses  develop.  They  are  not  like  the  particoloreds 
of  family  (8  x  54),  however,  for  in  the  cross  under  consideration 
seeds  with  the  gametic  formula  cP  do  not  develop  color.  The 
light  purples  behave  as  if  the  inhibiting  factor  could  vary 
zygotically  so  that  in  some  cases  light  purples  are  developed 
while  in  others  the  color  is  completely  inhibited,  and  also  as  if 
various  amounts  of  color  are  developed  in  the  presence  of  the 
inhibiting  factor  due  to  different  combinations  of  other  gametes. 
For  example,  it  seems  probable  that  more  color  may  be  developed 
in  the  presence  of  the  inhibiting  factor  when  the  zygote  is  homo- 
zygous for  the  purple  factor  than  when  it  is  heterozygous. 
Further  it  seems  less  likely  that  any  purple  color  develops  when 
the  inhibiting  factor  is  homozygous  than  when  it  is  hetero- 
zygous. This  makes  the  segregating  seeds  of  Fi  or  F2  ears 
very  difficult  to  classify  visually.  The  only  accurate  determi- 
nation of  the  gametic  structure  of  a  seed  is  through  its  own 
further  breeding. 

Fifteen  ears  of  Tom  Thumb  were  crossed  with  the  purple 
sugar  corn,  but  only  five  crosses  were  selected  from  which  to 
grow  the  Fo  generation.  One  of  these,  No.  60-5  x  54,  had  dark 
purple  and  non-purple  seeds,  while  the  other  four  crosses  had 
only  non-purple  or  very  light  purple  seeds.  It  was  a  little  un- 
fortunate perhaps  that  this  selection  was  made.  The  white  seeds 
in  cross  60-5  x  54  proved  to  be  selfed  Tom  Thumbs,  and  the  be- 
havior of  the  purple  hybrids  showed  that  no  inhibiting  factor  had 
been  present  in  ear  60-5.  The  behavior  of  the  crosses  made  on 
ears  60-2,  60-3,  60-8  and  60-11  showed  that  they  had  been 
homozygous  in  the  inhibiting  factor.  No  doubt  a  number  of 
the  other  crosses  would  have  shown  that  the  maternal  plants 
were  heterozygous  in  the  inhibiting  factor. 

For  these  reasons  the  data  from  cross  60-5  x  54,  which  may  be 
called  the  purple  family  (without  the  inhibiting  factor),  have 
been  listed  in  Table  24,  while  the  other  four  crosses  containing 
the  inhibiting  factor  are  shown  in  Table  25. 

The  resulting  F2  seeds  obtained  by  selfing  the  purple  Fi  seeds 
of  cross  60-5  x  54  shown  in  Table  24  were  purples,  reds  and  nqp.- 
purples.  No  light  purples  (particoloreds)  appeared  in  this 
family.  Splashed  purples  occurred  as  in  other  families,  but 
as  in  other  families  all  splashed  purples  were  heterozygotes 


INHERITANCE  OF  ALEURONE  COLOR.  83 

and  not  all  heterozygotes  were  splashed  purples,  showing  the 
phenomenon  to  be  due  —  as  before  —  to  incomplete  dominance 
caused  by  other  factors.  The  only  peculiar  thing  about  this 
cross  was  the  appearance  and  inheritance  of  the  red  color. 
The  extracted  reds  bred  true  apparently  and  were  hypostatic 
to  purple  as  in  other  families,  but  they  were  purplish  red  (dark 
magenta)  in  appearance  and  not  clear  reds  such  as  appear  in 
other  crosses.  It  is  conceivable  that  this  red  is  not  the  same 
red  that  appeared  in  the  other  crosses.  It  may  be  caused  by 
something  similar  to  what  Wheldale  (:  10)  has  suggested  may 
occur  in  stocks;  viz.  that  the  blue  oxygenase  may  act  in  con- 
junction with  the  red  peroxydase  or  vice  versa.  The  only 
difficulty  in  alining  the  results  obtained  with  the  ordinary 
behavior  of  the  known  factors,  is  the  fact  that  almost  none  of 
the  ears  of  the  F3  generation  show  the  same  ratios  as  the  F2 
generation. 

The  ratio  obtained  in  this  generation,  1843  purples:  188  reds: 
545  non-purples  immediately  suggests  12  :  1  :  3,  which  could 
be  obtained  from  Fi  seeds  with  a  formula  Pp  Xx  CC  RR  where 
X  is  an  inhibiting  factor  from  the  Tom  Thumb  which  affects 
R  but  not  P.  Our  failure  to  obtain  ears  in  F3  with  segregates 
of  9  purple;  3  red;  1  non-purple  caused  this  hypothesis  to  be 
discarded.  The  same  ratio  could  be  obtained  by  supposing 
that  there  is  a  partial  gametic  coupling  between  P  and  R  similar 
to  that  obtained  by  Bateson  and  Punnet  (:  08)  between  purple 
color  and  long  pollen  in  the  sweet  pea.  These  authors  suppose 
gametes  to  be  produced  after  the  general  formula  7  AB :  1  Ab : 
1  aB:  7  ab,  from  which  result  zygotes  3n2-(2n-l)  AB :  2n-l 
Ab:  2n-l  aB:  n2-(2n-l)ab.  Such  an  interpretation,  while  it 
may  represent  Bateson's  and  Punnett's  facts,  throws  no  light 
on  the  mechanics  of  heredity  for  there  is  no  reasonable  way 
known  at  present  for  such  a  segregation  to  come  about.  In 
our  own  case  *  no  such  excess  of  purples  was  obtained  in  the 
Fs  generation.  It  seems  better  therefore  to  consider  the  results 
of  the  F2  generation  in  the  light  of  the  breeding  records  of  the 
F3  generation.  If  this  is  done,  the  following  interpretation 
fits  the  facts  best.  Tom  Thumb,  the  female  parent  has  the 
gametic  formula  pcR,  and  Black  Mexican  the  male  parent  has 


*  Bateson  and   Punnett  have  never  reported   their  F3  generation  of 
sweet  peas,  although  they  state  that  it  gave  conflicting  results. 


84  INHERITANCE  IN  MAIZE. 

the  formula  PCR.  The  Fi  generation  is  therefore  PpCcRR. 
If  this  is  the  true  formula  there  is  the  following  theoretical 
expectation  in  the  F2  and  F3  generations : 


F2                    gives  in                        F3 

9 
Purple 

fl  P  P  C  C  R  R 
•2  P  p  C  C  R  R 
!2P  PCc  RR 
[4  P  p  C  C  R  R 

Pure  Purple. 
3  Purple  :  1  Red. 
3  Purple  :  1  Non-purple. 
9  Purple  :  3  Red  :  4  Non-purple 

3 

Red 

/I  CCRR 
\2  Cc  RR 

Pure  Red. 
3  Red  :  1  Non-purple. 

4 

Non-purple 

fl  PPRR 
2  P  p  RR 

U  P  P  c  c   R  R 

Pure  Non-purple. 
Pure  Non-purple. 
Pure  Non-purple. 

An  examination  of  the  F3  segregates  given  in  Tables  24a-e 
show  how  nearly  the  experimental  results  accord  with  the 
theory.  First  notice  that  out  of  55  ears  obtained  by  selfing 
purples  of  the  F2  generation,  20  segregated  purples  and  non- 
purples  without  reds.  This  is  more  than  our  own  theory  calls 
for  (theoreticall}^  12  out  of  55),  so  that  here  is  clear  evidence 
that  we  do  not  have  to  deal  with  partial  gametic  coupling  of 
the  kind  described  by  Bateson  and  Punnett.  But,  since  the 
deficiency  of  reds  in  the  Fo  generation  is  too  great  to  be  due 
to  chance  and  since  there  is  a  certain  excess  of  purples  in  the  F3 
generation,  we  must  say  frankly  that  we  are  dealing  with  some- 
thing that  we  cannot  yet  explain. 

The  entire  data  from  the  55  purple  F2  seeds  from  which  selfed 
ears  were  obtained  may  be  classified  as  follows:  8  ears  pure 
purple;  20  ears  segregating  purples  and  non-purples  in  the 
ratio  of  3  :  1 ;  9  ears  segregating  purples  and  reds  in  the  ratio  of 
3:1;  1  ear  each  segregating  purples  and  reds  in  ratios  of  5  :  1, 
6  :  1  and  12  :  1;  11  ears  segregating  purples,  reds  and  non- 
purples  in  the  ratio  of  9  :  3  :  4;  3  ears  segregating  purples, 
reds  and  non-purples  in  the  ratio  of  48  :  3  :  13  or  thereabouts. 

From  the  red  Fo  seeds  13  selfed  ears  were  obtained.  Out  of 
these,  3  were  pure  red  and  10  segregated  reds  and  non-reds  in 
about  the  ratio  of  3  :  1.  It-  should  be  remarked,  however,  that 
in  three  cases  the  heterozygous  reds  gave  a  greater  excess  of 
reds  than  usually  should  be  expected  with  chance  mating. 


INHERITANCE  OF  ALEURONE  COLOR.  85 

From  the  non-purple  F2  seeds  16  selfed  ears  were  obtained:  15 
were  pure  non-purple  while  one  gave  12  purples  to  49  non-purples. 
As  this  is  a  poor  ear,  the  12  seeds  may  be  due  to  foreign  pollen, 
or  a  chance  pollen  grain  possessing  the  inhibiting  factor  may 
have  produced  the  F2  white  seed  from  which  the  ear  resulted. 

With  the  plants  resulting  from  non-purple  F2  seeds  random 
intercrosses  were  also  made.  Of  these  13  gave  ears  with  all 
non-purple  seeds  and  one  gave  an  ear  with  49  purples  and  reds 
and  140  non-purples. 

These  results  generally  follow  our  theory  pretty  closely, 
but  there  are  abnormalities  difficult  to  explain.  We  seem  to  be 
dealing  with  only  two  heterozygous  factors  —  since  8  pure 
purples  are  obtained  from  55  ears  —  yet  tri-hybrids  and  tetra- 
hybrids  are  possible  which  give  such  results.  By  our  theory 
no  whites  should  give  purples  when  crossed  at  random.  One 
such  ear  occurred.  Was  it  an  error?  It  is  difficult  to  say. 
But  if  we  were  dealing  with  heterozygous  red  (Rr)  we  should 
expect  more  than  one  ear  out  of  14  to  give  purples  on  random 
crossing.  Furthermore,  it  can  be  seen  by  inspection  that 
there  are  many  reasons  why  we  cannot  be  dealing  with  simply 
a  heterozygous  red  factor.  It  is  not  denied  however  that 
several  other  unknown  factors  with  a  heterozygous  red  factor 
might  interpret  the  facts.  It  does  not  seem  possible  to  explain 
the  results  by  any  reasonable  system  of  gametic  coupling  or 
by  selective  mating.  P  and  C  certainly  are  present  in  an  heter- 
ozygous condition.  R  is  probably  homozygous  although  it  was 
not  found  in  the  Black  Mexican  in  other  crosses.  But  this  is  not 
peculiar  since  the  Black  Mexican  used  in  the  cross  can  only  be 
said  to  be  pure  for  purple.  On  the  other  hand,  the  red  does  not 
appear  to  the  eye  to  be  exactly  the  same  red  which  appeared  in 
the  other  crosses.  It  is  more  purplish  in  color,  as  if  it  were  a 
modified  purple.  Nevertheless  it  always  bred  true  after  ex- 
traction. 

Let  us  now  turn  to  what  may  be  called  the  white  side  of  this 
family.  As  was  stated  before  ears  60-2,  60-3,  60-8  and  60-11 
gave  no  dark  purples  when  crossed  with  No.  54.  (Some  seeds 
were  afterwards  found  to  be  very  slightly  purple.)  One  may 
conclude  therefore  that  they  (the  maternal  plants)  were  either 
homozygous  for  a  factor  that  inhibits  the  development  of  the 
purple  color;   or,  that  there  is  a  reversal  of  dominance,  which  is 


86  INHERITANCE  IN  MAIZE. 

improbable.  There  were  other  ears  that  gave  both  purple  and 
non-purple  seeds  in  crosses.  These  were  either  heterozygous 
for  an  inhibiting  factor  or  exhibited  dominance  of  both  purple 
and  non-purple  on  the  same  ear  which  is  still  more  improbable. 
None  of  these  ears  were  followed  into  the  F2  generation,  but 
progeny  of  all  four  of  the  ears  of  the  first  type  were  grown. 

The  results  of  the  F2  generation  from  these  ears  are  shown  in 
Table  25.  There  is  no  reason  why  some  of  these  families  might 
not  differ  from  others  in  invisible  factors,  for  different  plants 
of  No.  60  were  crossed  with  pollen  from  different  plants  of  No.  54. 
They  are  placed  in  one  table  here  but  certain  differences  in  their 
behavior  in  F3  leads  us  to  consider  them  separately.  There 
is  a  total  of  662  purples,  94  reds  and  2838  light  colored  purples 
and  non-purples.  The  reason  for  classing  the  light  purples 
and  non-purples  together  will  be  seen  later. 

The  results  of  the  F3  generation  as  well  as  our  experience  with 
other  crosses  are  such  as  exclude  the  possibility  of  a  reversal 
of  dominance.  The  purples  did  not  breed  true  nor  did  the 
behavior  of  any  of  the  classes  indicate  anything  other  than  a 
normal  Mendelian  segregation  involving  several  characters. 
Furthermore,  a  belief  in  reversal  of  dominance  in  our  opinion 
strikes  at  the  foundation  stone  of  Mendelism.  Not  that 
dominance  is  an  important  part  of  Mendelism.  It  is  not.  Yet 
no  analysis  can  be  made  of  breeding  records  without  following 
every  individual  for  several  generations  if  dominance  is  reversible. 
Of  the  thousands  of  extracted  recessives  that  have  bred  true, 
many  would  have  proved  to  be  heterozygous  dominants  if 
dominance  is  reversible. 

Taking  the  same  Fi  gametic  formula  that  served  for  the 
purple  side  of  the  family  and  adding  an  inhibiting  factor  I  which 
comes  from  No.  60,  gives  the  best  interpretation  of  the  data. 
This  makes  the  Fi  formula  PpCcIiRR.  In  F2  the  following 
classes  would  be  expected : 

Color  non-purple. 

"  non-purple. 

"  purple. 

"  non-purple. 

"  non-purple. 

"  non-purple. 

«  red. 

"  non-purple. 


J7  P  I   C  R 

9PI  R 

9PCR 

91  CR 

3PR 

31  R 

3CR 

1  p  c  i    r 

INHERITANCE  OF  ALEURONE  COLOR.  Sy 

The  ratio  is  9  purple  :  3  red  :  52  non-purple.  The  experimental 
results  given  in  Table  25  show  that  here  also  there  is  a  deficiency 
of  reds.  Many  light  purples  also  appeared,  but  these  were 
classed  as  non-purples.  This  was  done  because  in  Fs  the  light 
purples  behaved  as  if  they  possessed  the  factor  I  in  a  heter- 
ozygous condition,  the  variation  in  color  being  due  to  the  dif- 
ferent combinations  in  which  the  factors  P  and  C  appeared. 

With  this  theory  the  expectation  in  Fa  is  52  non-purples  and 
light  purples  giving : 

28  Producing  all  Non-purple  seeds. 

2  "  1  Purple  :  3  Non-purple. 

4  "  3  Purple  :  13  Non-purple. 

4  "  3  Purple  :  1  Red  :  12  Non-purple. 

8  "  9  Purple  :  3  Red  :  52  Non-purple. 

2  "  1  Red  :  3  Non-red. 

4  "  3  Red  :  13  Non-red. 

9  Purples  giving : 

1  Producing  all  Purple  seeds. 

2  "  3  Purple  :  1  Red. 

2  "  3  Purple  :  1  Non-purple. 

4  "  9  Purple  :  3  Red  :  4  Non-purple. 

3  Reds  giving : 

1  Producing  all  Red  seeds. 

2  "  3  Reds  :  1  Non-red. 

Let  us  now  examine  Tables  25a-e  which  give  the  results  from  selfing 
the  seeds  of  certain  of  the  F2  ears.  Table  25a  shows  the  progeny 
of  ear  (60-3x54)-l.  This  ear  gave  the  smallest  proportion 
of  purple  seeds  in  F2,  and  such  purples  as  were  produced  in  F2 
were  lighter  in  color  than  normal  full  purples.  In  F3  the  purples 
are  again  light  in  color.  They  are  classed  in  with  the  non- 
purples  in  the  last  column,  those  showing  some  color  being 
given  first.  The  first  two  ears  are  progeny  of  the  darkest 
purples;  one  has  purple  and  non-purple  seeds  in  the  ratio  of 
3  :  1  and  one  is  pure  purple.  The  next  two  ears  planted  from 
lighter  purples  show  a  difference  between  themselves.  One 
gives  3  light  purples  :  1  non-purple,  the  other  gives  1  purple  :  2 
non-purple.  The  latter  probably  came  from  an  ear  heter- 
ozygous for  the  inhibiting  factor  and  the  former  from  a  real 


88  INHERITANCE  IN  MAIZE. 

purple.  Of  those  ears  resulting  from  white  seeds,  one  has  33 
red  seeds  dark  enough  to  be  classed  as  real  reds  and  a  number  of 
very  light  reds  classed  with  the  non-purples  —  a  total  of  prob- 
ably near  25%  reds,  while  another  gives  light  purples  (and 
possibly  light  reds)  and  non-purples.  The  remaining  ears  are 
non-purples.  Five  plants  from  non-purple  F2  seeds  were  also 
crossed,  and  gave  all  non-purple  seeds.  In  reality,  however, 
only  two  random  crosses  can  be  said  to  have  been  made,  since 
the  pollen  of  No.  (60-3  x  54)-l-2  ES  was  used  three  times,  while 
once  the  same  plant  was  used  as  the  mother.  The  progeny  of 
ear  (60-3  x  54)-l,  therefore,  behave  like  those  of  other  ears  of 
this  family  except  that  all  of  the  progeny  of  purples  are  light  in 
color.  They  give  pure  purples  and  purples  segregating  into 
3  purples  :  1  non-purple,  but  none  are  dark  like  normal  purple 
ears.  Some  geneticists  would  probably  interpret  this  as  pre- 
potency of  the  non-purple  or  rather  lack  of  prepotency  of  the 
purple.  But  when  one  talks  of  prepotency  he  really  confesses 
ignorance  of  the  gametic  constitution  of  his  cultures.  Is  it 
not  much  more  likely  that  the  true  reason  for  the  production 
of  these  light  purples  lies  in  a  fact  more  in  keeping  with  what 
is  known  of  hereditary  phenomena?  May  not  one  say  that 
here  is  a  dominant  purple  character  coming  from  the  individual 
of  unknown  character  of  variety  No.  54  which  was  used  as  the 
male  parent  ?  If  the  purple  gene  from  the  male  parent  was  such 
as  to  give  always  a  lighter  purple  in  zygotic  combinations  where 
purple  is  visible  then  no  dark  purples  would  occur  in  the  segre- 
gates resulting  from  crosees.  Such  results  were  obtained  from 
four  selfed  plants.  Two  ears  resulted  from  planting  purples 
which  were  only  slightly  lighter  than  normal  dark  purples,  such 
as  the  parents  of  ears  (60-3  x  54)-l-l  and  (60-3  x  54)-l-2,  and 
two  ears  resulted  from  planting  seeds  quite  light  in  color.  (Table 
25a). 

Similar  results  were  obtained  from  cross  (60-8  x  54) ,  of  which 
the  Fs  generation  from  ear  (60-8  x  54) -8  are  shown  in  Table  25e. 
Here  eleven  ears  resulted  from  selfing  seeds  with  the  modified 
color  if  two  red  seeds  are  included.  None  of  these  ears  had 
seeds  dark  in  color,  but  the  ratios  are  no  doubt  the  same  as  those 
given  in  Tables  25  b-d.  The  general  reduction  of  the  amount 
of  purple  color,  however,  makes  the  error  of  classification  too 
great  for  safe  conclusions.     There  is  even  some  doubt  about 


INHERITANCE  OF  ALEURONE  COLOR.  89 

the  classification  of  the  seeds  from  the  F2  generation  of  these 
two  crosses  (Table  25),  but  the  results  of  the  F3  generation  are 
such  as  to  give  us  considerable  faith  in  them. 

Tables  25  b-d  give  a  considerable  number  of  F3  progeny  from 
F2  seeds  of  three  other  ears.  There  seems  to  be  no  reason  why 
they  should  not  be  considered  together.  From  the  purple  F2 
seeds  planted,  twelve  selfed  ears  were  obtained.  Three  ears 
were  pure  purples  of  the  normal  shade.  One  ear  gave  a  ratio 
of  3  purples  :  1  red  and  two  ears  a  ratio  of  3  purples  :  1  non- 
purple.  The  other  six  ears  gave  purple,  red  and  non-purple 
segregates.  Four  of  these  ears  were  clearly  of  the  ratio  9  :  3  :  4, 
but  in  the  remaining  two  there  was  a  considerable  deficiency 
of  red  seeds.  From  the  F2  red  seeds  planted,  only  one  selfed 
ear  was  obtained.  This  ear  gave  red  and  non-red  segregates  in 
the  ratio  of  3  :  1. 

A  large  number  of  selfed  ears  were  obtained  from  the  F2  light 
purple  and  non-purple  seeds.  Ears  of  each  of  the  classes 
expected  by  the  proposed  theory  were  obtained,  as  will  be  seen 
by  an  examination  of  the  Tables  25  b-d ;  but  as  the  visual  classi- 
fication is  arbitrary  owing  to  the  light  color  of  most  of  the  seeds, 
it  could  not  be  depended  upon  without  further  breeding.  The 
light  colored  seeds  are  given  first  in  the  last  column  of  the 
tables,  followed  by  the  seeds  which  were  apparently  non-purple. 
If  one  is  a  little  charitable  about  the  exactness  of  the  classifi- 
cation the  following  conclusions  can  be  drawn. 

Both  seeds  which  were  apparently  non-purple  and  seeds  which 
were  light  purple  in  color  in  the  F2  generation  gave  light  purple 
seeds  among  the  F3  segregates.  This  fact  proves  both  the  impos- 
sibility of  exact  classification  and  the  gametic  identity  of  seeds 
slightly  different  in  their  appearance. 

Two  plants  from  light  red  seeds  (Table  25b)  were  selfed. 
One  resultant  ear  showed  a  ratio  of  1  dark  red  :  3  light  red  and 
non-red;  the  other  ear  showed  only  light  red  and  non-red  seeds 
which  were  classed  together.  Thirty-six  plants  from  light  purple 
and  from  non-purple  F2  seeds  were  selfed.  Of  these,  fifteen 
ears  resulted  from  planting  seeds  classified  as  non-purple  in  F2. 
Only  four  of  them  threw  dark  purple  segregates  in  F2.  On  the 
other  hand  only  two  of  the  ears  resulting  from  selfed  plants 
which  were  progeny  of  seeds  classified  as  light  purples,  threw 
no  dark  purple  segregates.     It  seems  to  us  that  this  shows  a 


90  INHERITANCE  IN  MAIZE. 

fair  classification  of  seeds  heterozygous  for  the  inhibiting  factor' 
A  few  seeds,  however,  were  wrongly  classified  in  the  F2  genera- 
tion and  proved  their  proper  status  in  the  F3  generation. 

Out  of  the  total  of  36  selfed  ears  from  light  purple  and  non- 
purple  F2  seeds,  23  threw  dark  purple  segregates  and  13  produced 
only  light  purple  and  non-purple  seeds.  Of  those  ears  which 
threw  purple  segregates,  none  of  them  had  ratios  of  purple  to 
light  purple  plus  non-purple  greater  than  might  reasonably  be 
expected  by  chance  mating.  The  different  ratios  expected  in 
Fs  were  followed  rather  well,  although  it  is  recognized  that  these 
ratios  could  not  be  determined  accurately  with  such  small 
numbers. 


Conclusions. 

There  can  be  but  little  doubt  that  the  factors  I,  C,  P  and  R 
are  concerned  in  this  cross.  Whether  there  is  another  factor 
which  modifies  the  purple  color  or  not,  is  a  question  that  cannot 
yet  be  settled,  because  we  have  no  data  concerning  the  indivi- 
dual plant  of  No.  54  that  formed  the  male  parent;  yet  there 
seems  to  be  no  other  way  to  account  for  the  light  purples  in 
Table  25a  and  Table  25e.  The  ultimate  analysis  of  the  behav- 
ior of  the  R  factor  in  this  cross  must  also  be  left  in  abeyance. 
These  unsettled  questions  however  have  no  bearing  upon  two 
important  conclusions  which  the  evidence  forces  upon  us.  The 
first  is  that  one  should  be  exceedingly  careful  before  he  decides 
that  the  transmission  of  certain  characters  is  an  exception  to 
the  general  law  of  Mendel.  When  a  collection  of  white  or  non- 
purple  aleurone  strains  are  promiscuously  crossed  with  a  purple 
aleurone  maize,  the  results  seem  almost  impossible  to  bring 
into  conformity  with  simple  Mendelian  results,  yet  this  con- 
fusion is  brought  about  simply  by  the  gametic  differences  of 
the  non-purple  races.  If  such  confusion  can  result  in  the 
case  of  a  simple  color  inheritance,  much  more  care  must  be 
taken  to  analyze  the  transmission  of  more  complex  characters 
before  subsidiary  hypotheses  are  submitted. 

The  second  important  fact  is  in  regard  to  prepotency.  It 
has  been  shown  that  certain  families  of  purple  and  non-purple 
hybrids  produce  very  light  purples  when  P  exists  alone  without 
C,   while  other  families   produce   no   color.      No  modification 


INHERITANCE  OF  ALEURONE  COLOR.  91  j 

of  the  Mendelian  ratio  occurs,  yet  some  transmissible  difference  j 

in  the  two  families  gives  this  different  result.     Here  is  a  probable  | 

explanation  of  prepotency.     If  these  white  families  were  mixed  'i 

together,  a  mixture  more  easily  imagined  in  the  case  of  bisexual  | 

individuals,  there  would  appear  to  be  a  difference  in  prepotency  \ 

of   the   purple   character.     It  -therefore   seems   probable   that  i 

prepotency  is  due  only  to  a  difference  in  gametic  character  ; 

which  modifies  somatic  appearances  and  not  to  an  actual  modi-  1 

fication  of  Mendelian  chance  ratios  as  others  have  suggested.  \ 

The  behavior  of  the  other  families  is  so  simple  that  we  think  l 

there  can  now  be  no  question  but  that  the  purple  aleurone  color  ■ 

behaves  as  a  normal  Mendelian  character  in  inheritance.  1 


92 


INHERITANCE  IN  MAIZE. 


TABLE  24. 

F2   SEEDS   OF   CROSS   BETWEEN   NO.   60-5   NON-PURPLE   POP   AND 
NO.   54   PURPLE   SWEET. 

Purple  Seeds  Planted. 


Ear  No. 

Purple 

Red 

Non-Purple 

(60-5  X  54)-2 
(         "        )-3 
(         "         )-4 
(         "        )-5 
(         "         )-6 
(         "         )-8 

(      "      )-io 

(        "        )-ll 
(         "         )-12 

271 
236 
92 
203 
272 
144 
198 
190 
237 

28 
21 
11 
36 
33 
14 
21 
4 
20 

57 
71 
33 
69 
71 
58 
55 
55 
76 

Total 

1843 

188 

545 

TABLE  24A. 

F3   SEEDS   OF   EAR   NO.    (60-5  X  54)-2   OF   TABLE   24. 


E 

ar  No. 

Planted  from 

Purple 

Red 

Non- 
Purple 

(60-5  X  54 

-2-1 

Purple  S 

277 

23 

/        (f 

-2-2 

S 

16 

5 

C         " 

-2-3 

S 

176 

45 

69 

C          " 

-2-4 

s 

233 

48 

92 

(            " 

-2-1 

s 

209 

49 

72  , 

(            "            ^ 

-2-4 

s 

396 

(         " 

-2-1 

Red  S 

219 

91 

(            " 

-2-5 

"      S 

All 

/            u 

-2-1 

L.  Purple  S 

194 

27 

71 

(            " 

-2-2 

S 

167 

56 

80 

(           " 

-2-1 

Non-Pur.   S 

Pure 

/            (f 

-2-2 

S 

(( 

/            u 

-2-3 

S 

u 

(            " 

-2-4 

s 

u 

(           "            ^ 

-2-2  BS  X  2-1 

Red  X  Red  S 

380 

(            " 

-2-3  AO  X  2-2 

Pur.  X  Pur.   S 

280 

98 

(            " 

)-2-3  CS  X  2-1 

L.  Pur.  X  L. 

Pur.   S 

152 

37 

54 

(          " 

)-2-5  ES  X  2-4 

Non-Pur.  x 
Non-Pur.  S 

Pure 

(           " 

)-2-2  EO  X  2-1 

Non-Pur.  x 
Non-Pur.  s 

u 

INHERITANCE  OF  ALEURONE  COLOR. 


93 


TABLE  24B. 

F3  SEEDS  OF  EAR  NO.  (60-5  X  54)-6  OF  TABLE  24. 


Ear  No. 

Planted  from 

Purple 

Red 

Non- 
Purple 

(60-5  X  54 

)-6-3 

Purple   S 

87 

24 

38 

/        <f 

-6-4 

S 

204 

60 

(        " 

-6-6 

S 

262 

80 

/         « 

-6-7 

S 

318 

58 

/             u 

-6-4 

"         s 

265 

83 

(            " 

-6-1 

Red  S 

135 

29 

/            «            ^ 

-6-2 

"      S 

287 

76 

(            " 

-6-3 

"      S 

164 

48 

(            "            ^ 

-6-1 

"      s 

240 

71 

(            "            ^ 

-6-1 

Non-Pur.  S 

Pure 

/•           « 

-6-2  AS 

x4 

Pur.  x  Pur.  S 

384 

/•                 K                 ^ 

-6-5  AS 

x7 

S 

420 

(                 " 

-6-2  AG 

x3 

s 

200 

(                 " 

-6-2  ES 

xl 

Non-Pur.  x 
Non-Pur.  S 

Pure 

(     "     ; 

-6-4  ES 

x5 

(( 

u 

TABLE  240. 

F3  SEEDS  OF  EAR  NO.  (60-5  X  54)-8  OF  TABLE  24. 


Ear  No. 

Planted  from 

Purple 

Red 

Non- 
Purple 

(60-5  X 

54)-8-l 

Purple   S 

125 

(        " 

)-8-2 

S 

176 

55 

(        " 

)-8-3 

S 

212 

60 

(        " 

)-8-4 

s 

170 

/        ti 

)-8-6 

s 

183 

60 

(        " 

■     )-8-l 

s 

180 

28 

65 

(        " 

)-8-2 

s 

182 

35 

/         « 

)-8-5 

"         s 

153 

35 

/        « 

)-8-6 

s 

217 

71 

/         (( 

)-8-7 

s 

150 

(        " 

)-8-l 

Red  S 

176 

34 

/            u 

)-8-2 

"      S 

182 

(          " 

)-8-2 

"      s 

156 

57 

(          " 

)-8-l 

Non-Pur.  S 

180 

/            u 

)-8-4 

S 

12 

40 

(          " 

)-8-5 

S 

250 

/            « 

)-8-l 

s 

250 

(            " 

)-8-2 

s 

220 

C         " 

)-8-3 

"           s 
f  Non-Pur.  x  \ 
1  Non-Pur.  x  ] 

240 

(60-5  X 

54)-8-2  ES  x4 

400 

/  Non-Pur.  x  1 
1  Non-Pur.  x  J 

/         « 

)-8-7  ES  x6 

49 

140 

[  Non-Pur.  x  ) 

(         " 

)-8-4  EG  X  5 

i  Non-Pur.  x  [ 

220 

94 


INHERITANCE  IN  MAIZE. 


TABLE  24D. 

F3   SEEDS   OF   EAR   NO.    (60-5  X  54)-ll    OF  TABLE   24. 


Ear  No. 

Planted  from 

Purple 

Red 

Non- 
Purple 

[60-5  X  54 

)-ll-3 

Purple  S 

115 

42 

47 

1             u             > 

-11-4 

S 

175 

49 

c            u           > 

-11-5 

S 

175 

65 

((            > 

-11-6 

S 

180 

62 

«            ^ 

-11-8 

S 

209 

69 

'           If            > 

-11-10 

S 

210 

67 

r             li             > 

-11-11 

S 

101 

38 

((             ( 

-11-12 

«        S 

112 

39 

r             If             > 

-11-2 

«        s 

46 

21 

r             ((             ^ 

-11-3 

s 

144 

46 

If              ^ 

-11-4 

s 

178 

64 

«             ^ 

-11-7 

s 

180 

.    . . 

*             < 

-11-1 

L.  Purple  S 

116 

25 

49 

'              l(              ^ 

-11-3 

S 

204 

41 

75 

'              II              ^ 

-11-5 

S 

124 

52 

'              II              ^ 

-11-1 

s 

218 

29 

75 

'              «              1 

-11-2 

L.  Red   S 

163 

38 

If 

-11-1 

Non-Pur.   S 

Pure 

'              II              > 

-11-2 

"          S 

II 

11            ^ 

-11-5 

S 

II 

II 

-11-7 

S 

(f 

II            ■ 

-11-1 

s 

II 

11 

-11-2 

s 

(f 

60  X  54-5: 

-11-7  AS 

xll-6 

Pur.  X  Pur.   S 

142  Pur. 

and  Red 

56 

"        ) 

-11-3  ES 

xll-5 

Non-Pur.  x 
Non-Pur.   S 

Pure 

"        ) 

-11-6  ES 

xll-4 

Non-Pur.  x 
Non-Pur.   S 

(f 

"     ^ 

-11-2  EO 

xll-3 

II 

(f 

INHERITANCE  OF  ALEURONE  COLOR. 


95 


TABLE  24E. 

F3  SEEDS  OF  EAR  NO.  (60-5  X  54)-12  OF  TABLE  24. 


E 

ar  No. 

Planted  from 

Purple 

Red 

Non- 
Purple 

(60-5  X  54' 

-12-3 

Purple  S 

206 

78 

80 

(        "        ^ 

-12-4 

S 

201 

44 

67 

(        "        ^ 

-12-4a 

S 

350 

c        "        ^ 

-12-5 

S 

169 

59 

/       «       ^ 

-12-6 

S 

245 

65 

/        « 

-12-7 

s 

204 

67 

/       li 

-12-8 

s 

191 

49 

88 

(       " 

-12-9 

s 

187 

66 

(       " 

-12-10 

s 

239 

66 

/       « 

-12-13 

s 

248 

77 

(       " 

-12-14 

s 

217 

77 

(       " 

-12-1 

s 

240 

72 

/        « 

-12-3 

s 

350 

/        » 

-12-4 

s 

184 

43 

56 

(       " 

-12-5 

s 

300 

/       (1 

-12-7 

s 

147 

53 

/       (1 

-12-1 

Red  S 

229 

76 

("        " 

-12-3 

"      S 

280 

(       " 

-12-4 

"     s 

172 

56 

(       " 

-12-1 

Non-Pur.   S 

Pure 

(       " 

-12-8 

s 

a 

(60-5  X  54 

)-12-2  AS  X  3 

Purple  S 

lei 

56 

53 

(        " 

-12-11  As    x6 

S 

175 

63 

(        " 

-12-2    AG  X  1 

S 

229 

74 

(        " 

-12-3    ES  x5 

Non-Pur.   S 

Pure 

(        " 

-12-4    ES  x5 

S 

(t 

/        « 

-12-5    ES  x7 

S 

u 

/        « 

-12-7    ES  X  5 

S 

u 

/-        « 

-12-9    ES  x8 

S 

u 

o6 


INHERITANCE  IN  MAIZE. 


TABLE  25. 

F2    SEEDS    OF   CROSS    BETWEEN   NO.    60   NON-PURPLE   POP   AND   NO.    54 
PURPLE    SWEET. 

Very  Light  Colored  and  White  Seeds  Planted. 


Ear  No. 

Purple 

Red 

L.  Pur.  +  Non-Pur. 

(60-8  X  54)-l 

83 

5 

66 -f  135  =201 

(        "        )-7 

19 

7 

44  +  150  =  194 

(        "        )-8 

35 

4 

41+215=256 

(60-11  x54)-2 

22 

4 

22+  40=    62 

(60-2  X  54)-l 

68 

15 

96  +  159=255 

(        "        )-7 

86 

7 

99  +  150=249 

(      "      )-io 

89 

14 

69  +  148=217 

(60-3  X  54)-l 

26 

76+282=358 

(        "        )-3 

46 

7 

87+140=227 

(         "         )-.5 

54 

12 

102  +  159=261 

(        "        )-6 

65 

6 

113  +  144=257 

(        "        )-7 

69 

13 

117  +  184  =  301 

Total 

662 

94 

2838 

TABLE  25A. 

Fa    SEEDS    OF   EAR   NO.    (60-3  X  54)-l    OF   TABLE   25. 


Ear  No. 

Planted  from 

Pur. 

Red 

L.  Pur.  + 
Non-Pur. 

(60-3 

X  54)-l-l 

Purple  S 

235+  76=311 

)-l-2 

S 

245            =245 

)-l-l 

L.  Purple  S 

217+  69=286 

)-l-2 

S 

39+  72  =  111 

)-l-5 

Non-Pur.  S 

0+384=384 

)-l-6 

S 

105+204=309 

)-l-7 

S 

33L 

380* 

)-l-9 

S 

0+390  =  390 

)-l-10 

S 

0+280=280  1 

(        ' 

)-l-l 

"           s 

0+448=448 

(        t 

)-l-2 

"           s 

0+200=200 

)-l-3 

"           s 

0  +  152  =  152 

'         )-l-4 

"           s 

0+280=280 

(60-3 

X  54)-l-l  ES  X  1-2 

Non-Pur.  x 
Non-Pur. 

0+250=250 

/        < 

)-l-2  ES  X  1-1 

« 

0+258=258 

)-l-3  ES  X  1-2 

a 

0  +  110  =  110 

)-l-4  ES  X  1-2 

u 

0+308=308 

/        I 

)-l-8  ES  X  1-6 

u 

0+352=352 

Light  reds  and  non-reds. 


INHERITANCE  OF  ALEURONE  COLOR. 


97 


TABLE  25B. 

F3   SEEDS    OF   EAR   NO.    (60-3  X  54)-5    OF   TABLE   25. 


E 

ar  No. 

Planted  from 

Pu 

r.     Red 

L.  Colored  + 
Non-Colored 

(60-3  X  54 

)-5-l 

Purple  S 

16. 

5        47 

0+66    =66 

(        " 
(        " 
C         " 
(         " 

)-5-2 
-5-3 
)-5-4 
)-5-6 

"        S 
S 
S 
s 

25( 
20: 
30( 

27: 

) 

5        62 

) 

5 

"6+   95=    95 

/         « 

-5-1 

s 

17( 

3        13 

0+   69=    69 

(         " 

-5-1 

Red  S 

190 

0+  71=   71 

(         " 

-5-1 

L.  Purple  S 

'hi 

i 

136  +  110=246 

/         « 

-5-2 

S 

9( 

)        49 

115+  96=211 

/            u 

-5-2a 

S 

10^ 

t 

78  +  152=230 

(         " 

)-5-3 

S 

55 

) 

91+145=236 

(         " 

)-5-5 

S 

8( 

) 

58+  97  =  155 

(         " 

)-5-5a 

S 

7{ 

) 

65+   54  =  119 

I         " 

-5-6 

S 

88+  26  =  114 

/         « 

-5-4 

L.  Red  S 

( 

52 

78+  95  =  173 

(         " 

-5-2 

s 

75+  51=126 

(         " 

-5-2 

Non-Pur.  S 

0+352=352 

/         « 

-5-4 

S 

0+  30=   30 

/         « 

-5-7 

S 

'6' 

I 

138  +  193=331 

C         " 

)-5-8 

S 

0  +  380=380 

(          " 

)-5-9 

S 

0+345=345 

/            « 

-5-2 

s 

0+390=390 

(60-3  X  54 

)-5-l    ESx5-7 

Non-Pur.  x 
Non-Pur. 

125+313=438 

/        «        ^ 

-5-2    ESx5-4 

4' 

I 

14  +  126  =  140 

(        " 

-5-5    ESx5-4 

0+320=320 

/        « 

-5-10  ES  X  5-9 

90  +  154  =  244 

/            u 

-5-11  ESx5-9 

43+   87  =  130 

(          " 

-5-17  ES  X  5-7 

109  +  144=253 

/           « 

)-5-l    ESx5-5 

0  +  360=360 

/           u 

)-5-3    ESx5-4 

0  +  104  =  104 

(          " 

)-5-4    ESx5-3 

0+254=254 

r            " 

)-5-7    ESx5-5 

0+400=400 

INHERITANCE  IN  MAIZE. 


TABLE  25C. 

F3   SEEDS   OF   EAR   NO.    (60-3  X  54)-6   OF   TABLE   25. 


E 

ar  No. 

Planted  from 

p 

ur.     Red 

L.  Colored  + 
Non-Colored 

(60-3  X  54^ 

-6-2 

Purple  S 

1^ 

iO 

0-1-  71=   71 

(        " 

)-6-2a 

S 

1' 

75          9 

0+  64=    64 

(        " 

-6-5 

S 

1: 

38        20 

0-f  40=   40 

(        " 

-6-1 

L.  Purple  S 

31           5 

36-1-  38=   74 

(        " 

-6-la 

S 

-: 

19 

68+  49  =  117 

(        " 

-6-3 

S 

27 

53+  48  =  101 

(        " 

-6-4 

s 

( 

36         13 

63+  61=124 

(        " 

-6-6 

s 

{ 

36 

144  +  130=274 

(        " 

-6-1 

s 

' 

30 

108  +  142=250 

(        " 

-6-1 

Non-Pur.   S 

0+250=250 

(        " 

-6-3 

S 

25         '.'. 

70  +  106  =  176 

(        " 

-6-5 

s 

i 

21           3 

45+  62  =  107 

(        " 

-6-6 

s 

0  +  152  =  152 

(        " 

-6-7 

s 

( 

59         '.'. 

53  +  105  =  158 

(60-3  X  54 

-6-3  AS 

x6-2 

Pur.  x  Pur. 

^ 

51 

88+  80  =  168 

(        " 
(        " 

-6-1  AO 

)-6-2  ES 

x6-2 
x6-3 

Non-Pur.  x 

1^ 

] 

52         57 

L4 

'i5  +  '3r='46 

Non-Pur. 

(        " 

-6-3  ES 

x6-5 

« 

0+380  =  380 

(        " 

-6-5  ES 

x6-6 

li 

'.          *4 

21+117=138 

(        " 

)-6-6  ES 

x6-5 

(I 

17 

78  +  122=200 

(        " 

-6-7  ES 

x6-3 

11 

37  +  170=207 

(        " 

-6-8  ES 

x6-6 

u 

;     '4 

65+  61=126 

(        " 

)-6-2  EO 

x6-l 

11 

84+222=306 

(        " 

-6-4  EO 

x6-3 

il 

33+  26=   59 

(        " 

)-6-3  EO 

x6-4 

u 

t 

^6        25 

24  +  171=195 

PLATE    XI. 


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Inheritance  of  Aleurone  Color. 


i 


INHERITANCE  OF  ALEURONE  COLOR. 


991 


TABLE  25D. 

F3   SEEDS   OF   EAR   NO.    (60-8  X  54)-l    OF   TABLE   25. 


Ear  No. 

Planted  from 

Pur. 

Red 

L.  Colored  -|- 
Non- Colored 

(60-8  X  54)-l-6 

Purple  S 

135 

36 

0+  56=   56 

(        "        )-l-7 

S 

67 

16 

0+  20=   20 

(        "        )-l-3 
(        "        )-l-l 

s 
L.  Purple  S 

280 
20 

■66  +  '76  =  i42 

(         "         )-l-la 

S 

51 

i7 

63  +  164=227 

(         "         )-l-2 

S 

35 

1 

31+  84  =  115 

(         "        )-l-3 

S 

40 

20 

67  +  124=291 

(        "         )-l-5 

S 

20 

16 

27+  21=   48 

(         "         )-l-l 

s 

74 

101+115=216 

(         "         )-l-l 

Very  L.  Pur.   S 

92+121=213 

(         "         )-l-2 

S 

67 

5 

83  +  109  =  192 

(         "         )-l-4 

Non-Pur.    S 

0+250=250 

(         "         )-l-5 

s 

0+250  =  250 

(        "        )-l-6 

s 

0+230=230 

'(        "        )-l-7 

s 

0+240=240 

(60-8  X  54)-l-6    ES  x  1-7 

Non-Pur.  x 
Non-Pur.  S 

0  +  100  =  100 

(        "        )-l-7    ES  X  1-6 

11 

0+2.50  =  250 

(        "        )-l-8    ES  X  1-9 

11 

43+   66  =  109 

(        "        )-l-9    ES  X  1-8 

u 

151+158=309 

(        "        )-l-10  ES  X  1-9 

u 

68 

0  +  161=161 

(        "        )-l-l    EG  X  1-2 

Non-Pur.  x 
Non-Pur.   s 

0+240=240 

(        "        )-l-3    EG  X  1-7 

li 

K*  +  K    =1 

Approximated. 


.lOO 


INHERITANCE  IN  MAIZE. 


TABLE  25E. 

F3    SEEDS   OF   EAR  .NO.    (60-8  X  54)-8    OF   TABLE   25. 


Ear  No. 

Planted  from 

Pur. 

Red 

L.  Colored  + 
Non-Colored 

(60-8  X  54 

)-8-2 

Purple   S 

t54L 

236  +  100=336 

(        " 

)-8-5 

S 

212+     0  =  212 

(        " 
(        " 

)-8-l 
)-8-2 

Red  S 
"      S 

266L 
5L 

■26  +  "8  =  '34 

(        " 

)-8-l 

L.  Purple  S 

110  +  104  =  214 

/        « 

)-8-2 

S 

224  +  123=347 

(        " 

)-8-5 

S 

50  +  148  =  198 

(        " 

)-8-7 

S 

62L 

0+248=248 

(        " 

)-8-8 

S 

7bL 

84  +  164=248 

/            a 

)-8-l 

s 

90+202=292 

(           " 

)-8-l  lower  ear 

"            s 

97+243=340 

(           " 

)-8-3 

Non-Pur.   S 

80  +  294  =  374 

(           " 

)-8-9 

S 

80+216  =  296 

(" 

)-8-2 

'      "         s 

37L 

0+263=263 

(60-8  X  54 

)-8-l  ES  X  8-7 

Non-Pur.  X 
Non-Pur.  S 

0+300=300 

/            a 

)-8-2  ES  X  8-3 

S 

39+260=299 

(           " 

)-8-4  ES  X  8-9 

S 

49+214  =  263 

/            « 

)-8-5  ES  X  8-17 

S 

0+200=200 

/            « 

)-8-6  ES  X  8-9 

S 

0+300=300 

/            « 

)-8-7  ES  X  8-17 

S 

24+270=294 

(           " 

)-8-l  EO  X  8-2 

s 

88  +  174=262 

/            <( 

)-8-5  EO  X  8-3 

s 

48*  +  153=201 

*  Several  seeds  rather  dark  purple. 

t  Those  marked  L  are  light  in  color  but  not  nearly  as  light  as  those 
given  in  the  last  column. 


PLATE   XII. 


Xo.  21.     Pod.k-il  maize.  b.     No.  7,  non-podded  maize. 


f  ^-*,-4.''iN.vV^ 


qK- 


■c.     Cru-..-  Jix;.     I- ^  aljoxt'i  pud  cliaractcr  tull\-  domniant.  Fj  below:   com- 
plete segregation  in  monohybrid  ratio. 

Inheritance  of  "Podded"  Character. 


XENIA.  loi 


PART  III. 

XENIA. 

The  appearance  of  the  endosperm  in  the  Fi  generation  in  the 
crosses  discussed  in  Part  II  really  include  almost  all  of  our 
observations  of  true  Xenia,  but  the  subject  is  sufficiently  import- 
ant to  warrant  a  more  systematic  arrangement  of  the  facts. 

The  word  Xenia  was  proposed  by  Focke  to  denote  the  effect, 
if  any,  produced  by  the  action  of  pollen  upon  the  maternal 
tissue  of  the  seed  plant.  The  classical  example  of  such  effect 
was  the  endosperm  of  maize.  After  the  discovery  by  Guignard 
('99)  and  Nawaschin  ('99)  that  the  endosperm  is  in  reality  a 
part  of  the  filial  generation  formed  by  the  development  of  the 
endosperm  nucleus  after  fusion  with  the  second  male  nucleus 
of  the  pollen  cell,  De  Vries  ('99),  Correns  ('99)  and  Webber  ( :  00) 
saw  in  this  the  explanation  of  the  phenomenon  in  maize.  These 
facts  took  away  the  only  authentic  illustration  of  Xenia  in  its 
original  use  —  the  effect  of  foreign  pollen  on  matern^,!  tissue. 
In  this  older  sense  the  word  is  therefore  of  no  value,  and  it  may 
be  used  solely  to  describe  the  visible  effect  of  the  second  male 
nucleus  on  the  endosperm.  Unfortunately,  botanists  have  not 
been  so  prompt  in  discarding  belief  in  the  original  meaning  of 
Xenia  as  the  zoologists  in  discarding  telegony.  In  the  experi- 
ence of  Correns,  of  Lock  and  of  ourselves  the  effect  of  the  second 
male  nucleus  has  never  extended  to  maternal  tissue.  One 
of  the  present  authors  has  made  several  experiments  in  which 
pollination  without  fertilization  (between  infertile  species)  has 
had  an  effect  on  maternal  tissue,  (parthenocarpie) ,  but  this 
effect  was  simply  that  of  a  chemical  stimulus  or  irritant  produc- 
ing cell  division  in  the  carpels. 

The  visible  effects  of  double  fertilization  have  been  found 
in  the  following  cases,  in  all  of  which  the  parents  have  been 
selfed  strains  that  precluded  errors  in  the  observations.  Non- 
starchy  seeded  plants  crossed  with  starchy  seeded  plants  always 


102  INHERITANCE  IN  MAIZE. 

show  starchiness.  Starchiness  is  completely  dominant,  there- 
fore the  reciprocal  cross,  bringing  in  the  "opposing"  character, 
never  shows  Xenia. 

Yellow  endosperm  is  also  completely  dominant  in  most  cases. 
Non-yellow  crossed  with  yellow  endosperm  therefore  shows 
Xenia  while  the  reciprocal  shows  no  Xenia.  Three  exceptions 
to  this  rule  were  found,  however.  In  the  large  races  of  dent 
maize  where  the  zone  of  soft  starch  at  the  summit  of  the  seed 
is  extensive,  the  heterozygous  yellow  is  somewhat  lighter  in 
color  than  the  homozygous  yellow,  and  Xenia  appears  when 
the  cross  is  made  either  way.  It  shows  as  a  cap  of  lighter  color 
than  the  homozygous  yellow.  When  floury  yellow  races  are 
crossed  with  floury  white  races  this  lighter  color  of  the  heter- 
ozygote  extends  throughout  the  seed.  In  this  case  difference 
in  color  is  always  great  enough  to  be  noticed  by  a  careful  observer 
in  either  cross,  but  where  the  cap  only  is  floury  the  color  inter- 
grades  to  that  of  the  homozygous  yellow.  When  dealing 
with  races  with  corneous  endosperms,  such  as  the  flint  and  pop 
varieties,  there  is  so  little  difference  in  color  that  the  homo- 
zygous yellow  is  generally  indistinguishable  from  the  heter- 
ozygous yellow;  therefore  Xenia  occurs  only  when  the 
white  is  the  female  parent.  Even  here,  however,  we  have 
found  two  different  cases  where  a  few  heterozygous  yellows 
were  distinguishable  from  homozygous  yellows  when  the  latter 
were  used  as  the  female. 

Both  the  red  and  the  purple  colors  in  the  aleurone  cells  behave 
in  the  same  way  as  regards  Xenia.  When  the  two  parents 
differ  only  in  these  characters,  they  are  completely  dominant 
and  Xenia  occurs  only  when  they  are  possessed  by  the  male 
parent.  Even  in  the  race  in  which  a  slight  purple  color  appeared 
when  the  color  factor  was  absent  (P  c  instead  of  P  C)  the  same 
slight  color  appeared  when  it  was  used  as  the  male  upon  a  race 
in  which  P  and  C  were  both  absent.  Furthermore  when  this 
race  was  crossed  either  way  with  a  white  race  bearing  the  color 
factor  (PcxpCorp  CxPc),  the  full  purple  developed  and 
appeared  as  Xenia.  The  red  color  undoubtedly  behaves  in 
the  same  way  although  we  have  made  no  original  crosses  deal- 
ing with  these  conditions.  Again,  two  pure  white  races  (P  c 
and  p  C)  which  show  not  the  slightest  color  may  bring  together 


XENIA.  103 

the  two  factors  P  and  C  necessary  for  full  development  of  the 
purple  color,  and  Xenia  results  when  either  is  the  female  parent. 

The  next  and  last  case  in  which  we  have  observed  Xenia  is 
that  in  which  the  white  parent  possesses  a  character  that  inhibits 
the  development- of  red  or  purple  aleurone  cells.  Correns  and 
Lock  probably  used  races  containing  this  character  but  they 
did  not  distinguish  it  from  a  recessive  white  or  simple  absence 
of  the  purple  character.  They  therefore  concluded  that  when 
a  white  race  was  crossed  with  a  purple,  Xenia  sometimes  results 
and  sometimes  does  not  result,  and  that  no  change  occurs  when 
the  purple  is  the  female  parent.  The  true  state  of  affairs  is 
just  the  opposite  of  this.  When  a  white  containing  the  inhibi- 
tor is  the  male  parent,  a  white  seed  results,  and  while  the  same 
result  is  obtained  in  the  reciprocal  cross  it  is  of  course  unnoticed 
when  the  white  is  the  female  parent.  Sometimes  the  purple 
is  not  fully  inhibited  and  then  a  light  purple  results  no  matter 
which  parent  is  the  mother. 

If  one  considers  these  observations  as  a  whole,  the  following 
law  regarding  Xenia  may  be  formulated : 

When  two  races  differ  in  a  single  visible  endosperm  character  in 
which  dominance  is  complete,  Xenia  occurs  only  when  the  dominant 
parent  is  the  male;  when  they  differ  in  a  single  visible  endosperm 
character  in  which  dominance  is  incomplete  or  in  two  characters 
both  of  which  are  necessary  for  the  development  of  the  visible  dif- 
ference, Xenia  occurs  when  either  is  the  male. 

Correns  observed  that  in  every  case  where  Xenia  may  be 
expected  to  occur,  the  seeds  showing  Xenia  were  always  hybrids. 
This  fact  was  assumed  to  prove  that  the  second  male  nucleus 
always  bears  the  same  characters  as  the  one  that  fuses  with 
the  egg  cell  to  form  the  embryo.  For  this  reason  Mendelian 
segregation  of  the  gametes  must  have  occurred  previous  to  the 
division  of  the  pollen  nucleus.  Our  observations  are  entirely 
in  accord  with  those  of  Correns.  The  latter  author  and  also 
Webber  observed  several  cases  where  Xenia  occurred  in  only 
one-half  of  the  endosperm.  These  rare  phenomena  which  are 
probably  similar  in  nature  to  the  gynandromorphs  occurring 
in  insects,  they  both  interpreted  as  the  independent  develop- 
ment of  the  endosperm  nucleus  and  the  second  male  nucleus. 
We  have  observed  many  instances  of  this  phenomenon  and 
have  grown  a  number  of  them  to  see  if  the  tendency  was  inherited 


T04  INHERITANCE  IN  MAIZE. 

but  without  positive  results.  Correns'  and  Webber's  expla- 
nation of  the  cause  of  these  seeds  is  probably  correct,  yet 
the  suspicion  cannot  be  avoided  that  if  the  two  nuclei  can 
develop  independently  then  the  female  nucleus  ought  some- 
times to  develop  to  the  total  exclusion  of  th-e  male.  If  this 
were  true  a  seed  showing  no  Xenia  where  it  is  to  be  expected, 
should  sometimes  prove  to  be  a  hybrid.  This  has  never  occurred 
in  our  work,  a  fact  in  disagreement  with  the  work  of  Webber. 
It  may  be  possible  then  that  the  cause  of  these  seeds  is  Mende- 
lian  segregation  in  somatic  tissue,  such  as  often  occurs  in  bud 
sports.  This  could  be  proved  if  there  occurred  among  the  Fi 
seeds  of  a  cross  in  which  the  parents  differed  in  two  characters, 
an  individual  in  which  the  characters  were  segregated  dif- 
ferently: for  example,  if  a  white  sweet  maize  were  pollinated 
with  a  yellow  starchy  race,  and  a  seed  developed  having  one 
half  yellow  sweet  and  the  other  half  white  starchy.  The  matter 
is  simply  mentioned  because  it  is  important  to  biological  theory, 
and  it  was  thought  that  some  experimentalist  might  happen 
upon  such  an  individual. 

It  is  thought  that  Webber's  idea  that  seeds  with  splashed 
purple  aleurone  cells  are  due  to  mosaic  development  of  cell 
descendants  of  the  endosperm  nucleus  and  of  the  second  male 
nucleus,  is  incorrect.  If  this  idea  were  true,  in  cases  where  the 
endosperm  is  heterozygous  yellow,  this  character  also  should 
be  mosaic.  Such  cases  have  never  been  reported.  It  therefore 
seems  better  to  consider  the  splashed  purples  as  cases  of  incom- 
plete dominance  caused  by  other  factors  as  was  explained  in 
greater  detail  earlier  in  the  paper. 


PLATE     XIII. 


a.     Podded  maize.     The   four  husks  successively  removed   showing  naked 
seed    at    right.        The    double    rowed   condition    characteristic     of     all 
maize  varieties  is  seen  most  clearlv. 


Male  spikes  (tassels)  showing  development  of  seeds,  b.  a  dominant  F2 
plant;  c,  a  recessive  F2  plant.  Segregation  is  persistent  in  this  cross, 
21x7. 


Inheritance   of   "Podded"   Character. 


I 


PLATE    XIV. 


t  left,  the  color  which  develops  in  sunlight — R4;  in  center  variegated 
or  mosaic  seeds — R2;  at  right,  common  red  pericarp — Ri. 


fl.     At  left,  the  cok 


b.  Segregation  of  pericarp  color  R4  in  F2  of  cross  5x11.  Amount  of  color 
developed  is  variable  depending  on  light  conditions  during 
maturation. 


Pericarp  Colors. 


INHERITANCE  OF  POD  CHARACTER.  105 


PART  IV. 


PLANT    CHARACTERS. 


In  this  part  of  the  paper  the  inheritance  of  normal  plant 
characters  is  considered.  These  characters  in  general  have  no 
effect  upon  the  endosperm  —  the  new  generation  —  and  there- 
fore do  not  show  as  Xenia  in  the  daughter  seeds  of  the  ear  that 
has  been  crossed. 

Podded  and  Podless  Maize. 

The  inheritance  of  the  podded  character  is  interesting  because 
it  is  a  shining  example  of  a  case  where  a  gross  morphological 
character  behaves  as  a  simple  Mendelian  mono-hybrid.  No. 
21  a  podded  maize  was  crossed  with  a  common  Learning  dent 
like  No.  7,  but  not  of  the  same  stock.  The  Fi  generation  was 
as  perfectly  podded  as  the  podded  parent.  There  was  of  course 
some  variation  in  the  length  of  the  husks  of  the  seeds,  a  varia- 
tion apparently  physiological  in  character  depending  upon  the 
vigor  of  the  mother  plant,  but  this  variation  was  no  greater 
in  the  Fi  generation  than  it  was  in  the  pure  podded  maize.  The 
F2  generation  yielded  64  podded  and  21  non-podded  individuals. 
The  latter  were  without  any  trace  of  husk  and  were  not  dis- 
tinguishable from  ordinary  non-podded  corn  which  had  never 
been  crossed  with   a  podded  variety.     (See  Plate  XII.) 

The  Fi  generation  was  also  crossed  back  with  the  recessive  — 
the  non-podded  variety  —  and  in  the  next  generation  yielded 
41  podded  ears  and  50  non-podded  ears.  In  other  words 
Hh  X  h  gave  50%  Hh  and  50%  hh  as  was  to  be  expected. 
The  character  was  again  strictly  discontinuous.  The  extracted 
recessives  proved  absolutely  true. 

Pericarp  Color. 

There  are  various  red  sap  colors  appearing  in  the  pericarp, 
the  cob,  the  husks,  the  silks,  the  glumes  and  the  anthers  of  maize. 
We  have  not  been  able  to  make  a  chemical  study  of  them  and 


io6  INHERITANCE  IN  MAIZE. 

so  cannot  say  if  they  are  due  to  the  same  compound,  but  the 
comparatively  small  amount  of  data  regarding  their  inheritance 
that  we  have  obtained  is  particularly  interesting  on  account  of 
the  number  of  different  organs  in  which  color  occurs.  It  has 
long  been  thought  that  such  colors  that  manifest  themselves 
in  different  parts  of  a  plant,  are  single  units  as  regards  heredity, 
but  are  produced  in  visible  quantities  only  when  developmental 
conditions  are  favorable  or  when  certain  transmissible  limiting 
factors  or  extension  factors  which  effect  their  development, 
are  present  or  absent.  Our  especial  problem  was  to  find  out 
whether  these  red  colors  occurred  and  were  transmitted  separately 
or  whether  they  were  linked  together  in  genetic  or  in  chemical 
relationships.     This  work  is  therefore  simply  a  report  of  progress. 

The  first  red  pericarp,  which  we  will  call  Ri  was  found  in 
No.  27,  a  rice  pop  maize.  It  was  the  ordinary  dark  red  color 
of  the  varieties  commonly  known  as  red  corns.  It  did  not 
have  a  red  cob  or  red  silks,  although  the  glumes  of  the  male 
flowers  were  sometimes  reddish.  Crossed  with  number  28,  a 
rice  pop  with  white  pericarp,  white  cob  and  silks,  it  gave  75  red 
and  22  white  ears  in  F2.  The  color  was  inherited  absolutely 
discontinuously,  the  reds  being  all  dark  and  the  whites  showing 
no  trace  of  color. 

The  only  other  cross  with  apparently  this  same  dark  pericarp 
color,  was  a  peculiar  ear  found  in  a  field  of  dent  maize  of  unknown 
parentage.  This  ear,  as  shown  in  Plate  XV,  fig.  a,  had  seeds 
with  red  pericarp  on  one  side  and  seeds  which  were  sometimes 
white  and  sometimes  striped  with  red  on  the  other  side.  The 
ear  appeared  in  a  field  of  white  maize  in  which  only  white  maize 
was  planted.  It  must  have  been  produced  therefore  by  a 
hybrid  seed  Ri  ri.  Furthermore  since  it  was  the  only  ear  in 
the  field  showing  red  pericarp,  it  is  likely  that  it  was  nearly  all 
pollinated  by  white.  One  would  expect  its  seeds  therefore  to 
be  half  Riri  and  half  riri,  and  that  they  would  give  in  the  next 
generation  50%  red  ears,  50%  white  ears.  In  order  to  test 
any  possible  transmission  of  the  variation  which  appeared  in 
this  ear  however,  both  the  red  seeds  and  the  seeds  from  the 
side  which  had  white  and  striped  kernels  were  planted.  From 
the  dark  red  seeds  were  obtained  22  dark  red  ears  and  22  white 
ears;  from  the  white  and  striped  seeds  were  obtained  15  ears 
showing  a  few  red  striped  seeds  and  15  ears  with  only  white 


INHERITANCE  OF  PERICARP  COLOR.  107 

seeds.  No  difference  was  observed  between  the  progeny  of 
white  and  of  striped  seeds.  Both  kinds  of  seeds  from  this  side 
of  the  ear  gave  striped  ears  and  white  ears.  A  selfed  red  ear  of 
this  generation  gave  a  simple  mono-hybrid  ratio  in  the  next 
generation  —  75  red  ears  and  26  white  ears.  The  explanation 
of  this  phenomenon  evidently  is  the  same  as  that  of  the  bud 
variations  that  sometimes  occur  in  perennials.  They  occur  in 
annuals  but  are  usually  unnoticed.  The  plant  due  to  produce  a 
red  ear  varied  somatically  so  that  one-half  of  the  ears  was  red  and 
one-half  striped.  This  variation  was  transmitted  by  seeds, 
but  at  the  same  time  the  hybrid  character  of  its  seeds  was 
unchanged  as  shown  by  their  segregation  into  reds  and  whites 
in  the  next  generation  and  the  normal  segregation  of  the  hybrid 
dark  reds  in  a  further  generation.  This  strain  had  red  cobs, 
and  there  was  perfect  coupling  between  the  two  characters  in 
the  next  generation. 

Two  other  red  pericarp  colors  seemingly  independent  of  red 
in  other  parts  of  the  plant  have  been  found,  which  may  be 
called  R2  and  R3.  R2  is  a  dark  red  that  occurs  as  irregular  red 
stripes  radiating  from  the  point  where  the  silk  was  attached; 
R3  is  a  dirty  red  color  more  abundant  at  the  base  of  the  seed 
and  almost  wanting  at  the  summit.  The  dye  occurs  in  small 
amounts.  The  latter  red,  which  occurs  in  Palmer's  red-nosed 
yellow  appears  to  be  completely  coupled  *  with  red  silks.  It 
is  almost  certain  that  this  red  forms  an  allelomorphic  pair  with 
its  absence  that  is  entirely  independent  of  Ri,  R2  and  R4,  but 
our  numbers  are  too  small  to  make  a  full  report  on  the  matter. 
The  mosaic  red  (R2)  is  also  one  that  has  not  been  subjected  to 
sufficient  genetic  study.  Thus  far  (2  generations)  it  has  not 
bred  true  but  has  thrown  a  percentage  of  non-reds. 

Two  other  red  pericarps  have  occurred,  however,  which  are 
interesting  because  they  are  the  same  in  appearance  but  are  not 
allelomorphic  to  each  other.  The  first  is  a  rose  red  (R4)  charac- 
teristic of  No.  5.  It  develops  only  in  presence  of  light,  hence 
the  ears  with  thick  husks  show  the  color  but  faintly.  When 
the  husks  are  stripped  away  and  the  ear  matures  in  full  sun- 
light, however,  the  color  appears  over  the  entire  ear  as  a  bright 


*  Coupling  is  proved  by  the  fact  that  red  silks  occur  without  red  peri- 
carp in  other  combinations. 


io8  INHERITANCE  IN  MAIZE. 

rose  red.  In  numbers  2,  8  and  18  there  appeared  another  red 
which  we  at  first  thought  was  the  same  as  the  above.  It 
occurs  in  less  amounts  and  on  thick-husked  ears  can  only  be 
detected  by  careful  examination.  Since  these  two  reds  behave 
as  separate  allelomorphic  pairs  they  are  called  R4  and  Rg. 

The  transmission  of  these  two  reds  was  shown  by  crossing 
No.  5  (R4)  with  No.  18  (Rs).  In  Fi  all  of  the  ears  were  red.  In 
F2  there  were  131  red  ears  and  7  white  ears.  No.  5  (R4)  was  also 
crossed  with  No.  2  (Rs)  and  gave  similar  results  although  the 
number  of  plants  was  small.  In  F2  there  were  52  red  ears  and 
2  white  ears. 

It  may  be  asked  whether  the  red  in  No.  5  (R4)  acts  as  a  simple 
mono-hybrid  in  crosses  with  strains  having  no  red  in  the  peri- 
carp. We  have  only  one  cross  of  this  kind  in  which  data  for 
pericarp  color  were  taken.  No.  11-2  (r4)  was  crossed  with  No. 
5  (R4)  and  yielded  251  red  ears  and  91  white  ears  in  F2. 

None  of  these  varieties  had  the  red  color  in  other  organs. 

Cob  Color. 

Several  crosses  were  made  in  which  one  parent  had  a  red  cob 
and  one  a  white  cob.  None  of  the  parents  had  dark  red  peri- 
carps (Ri)  but  in  one  case  R4  was  present  (the  light  red  pericarp 
developing  in  presence  of  light).  In  a  cross  between  No.  5 
and  No.  6,  F2  yielded  277  ears,  of  which  212  had  red  cobs  and 
65  white  cobs.  It  was  strictly  a  mono-hybrid  cross,  and  the 
character  red-cob  seemed  not  to  be  coupled  with  the  pericarp 
color.     This  red  we  may  call  Re. 

The  parents  in  this  case  were  tested  for  purity  although  there 
are  strains  of  No.  6  in  our  possession  that  do  not  have  red  cobs. 
The  results  of  the  other  crosses  were  similar  and  space  will  not 
be  taken  to  report  them  in  full.  It  must  be  noted  however,  that 
although  no  di-hybrid  reds  were  found,  it  is  not  beyond  prob- 
ability that  such  might  be  found  in  an  extensive  series  of 
crosses. 

Silk  Color. 

Varieties  are  also  obtained  which  have  red  silks  although  the 
red  color. is  not  manifested  in  other  parts  of  the  plant.  In  fact, 
No.  19,  which  has  the  darkest  red  silks  of  any  variety  in  our  pos- 


PLATE     XV 


a.     Somatic  or  bud  variation  from  dark  red  seeds  to  slightly  variegated 
seeds  in  ear  whose  seeds  were  supposed  to  be  half  R^,  ri,  and  half 

ri,  rj. 


b.     Progeny  of  red  seeds  of  a.    Half 
dark  red,  half  white. 


Progeny  of  sliglulx  \ariegated 
seeds  of  a.  Half  slightly  var- 
iegated, half  white. 


d.     Similar  bud  variation  in   which  R2  is  concerned. 
Pericarp    Colors   and   Somatic    Segregation. 


DISCUSSION  OF  SAP  COLOR.  109 

session,  has  white  cob  and  pericarp.  It  is  not  quite  clear,  how- 
ever, how  this  character  is  transmitted.  The  facts  are  obscured 
by  the  action  of  the  bag  over  the  ear  to  be  hand-poUinated, 
which  prevents  the  full  development  of  the  red  color  by  shutting 
out  the  light.  For  this  reason  one  cannot  be  certain  whether  the 
Fi  plants  which  are  selfed  are  full  reds  or  only  red-haired  silks. 
An  illustration  of  what  is  obtained  in  a  cross  between  red 
silk  and  non-red  silk  varieties  is  as  follows.  No.  12-2  which  is 
pure  fof  non-red  silks  was  crossed  with  No.  9-2  which  is  pure 
for  red  silks.  In  Fi  there  were  110  plants  with  red  silks  and  27 
with  greenish- white  silks  with  red  hairs.  In  F2  the  progeny  of 
3  Fi  plants  were  grown.  The  first  ear  gave  123  plants  with  red 
silks  and  40  with  white  silks.  The  progeny  of  the  other  two  ears 
were  of  three  classes;  reds,  greenish-whites  with  red  hairs  and 
greenish-whites  in  the  numbers  198  :  29  :  94.  We  will  not 
attempt  to  analyze  this  ratio.  It  is  simply  mentioned  to  show 
that  the  silk  color  does  mendelize  without  the  production  of 
color  in  other  parts  of  the  plant. 

Glume  Color. 

No  plant  has  yet  been  obtained  which  has  red  glumes  and  yet 
shows  no  red  color  in  other  parts  of  the  plant.  One  has  been 
found  however  that  is  pure  for  red  glumes  and  shows  no  red  in 
other  parts  with  the  exception  of  the  silks. 

General  Consideration  of  Red  Sap  Color. 

It  is  difficult  to  put  aside  the  thought  that  all  of  these  red 
colors  are  localizations  of  the  same  general  pigment.  If  this 
were  true,  there  should  be  a  series  of  varieties  in  which  increas- 
ing extension  of  color  is  found,  until  red  appears  in  all  the 
organs  in  which  it  ever  occurs.  This  is  not  true.  Varieties 
exist,  for  example,  with  red  pericarp  and  red  cob,  with  red  peri- 
carp and  white  cob  and  with  white  pericarp  and  red  cob.  If 
these  formed  a  series  with  increasing  extension  of  red  one  might 
find  the  color  localized  in  the  cob  and  not  found  in  the  pericarp, 
but  the  theory  could  not  account  for  the  existence  of  varieties 
with  red  pericarp  and  white  cob.  It  seems  as  if  these  facts 
would  drive  us  to  one  of  two  conclusions.     We  are  dealing. 


no  INHERITANCE  IN  MAIZE. 

either  with  different  color  compounds  each  of  which  manifests 
itself  in  only  one  organ,  or  with  identical  genes  held  in  the  germ 
cells  in  such  different  combinations  that  they  may  be  mani- 
fested differently.  The  latter  interpretation  is  more  probable, 
and  the  natural  assumption  is  that  identical  genes  held  by 
different  chromosomes  in  some  way  accounts  for  the  different 
manifestations.  Yet  there  is  an  obstacle  to  this  assumption 
which  though  not  necessarily  insurmountable,  is  at  least  impor- 
tant. One  cannot  quite  understand  why  a  red  color  should  be 
manifested  in  different  organs  simply  because  its  gene  is  held  by 
different  chromosomes. 

Since  the  first  draft  of  this  paper  was  written  Emerson  *  has 
reported  important  data  from  many  crosses  where  certain  of  these 
red  colors  of  maize  are  sometimes  absolutely  coupled  in  their 
inheritance  and  sometimes  show  spurious  allellomorphism.  For 
example,  if  a  plant  with  a  red  cob  and  a  red  pericarp  is  crossed 
with  one  in  which  these  colors  are  absent,  there  is  segregation 
in  F2,  but  the  colors  remain  together.  On  the  other  hand,  if 
a  cross  is  made  between  a  plant  having  a  red  cob  and  a  white 
pericarp  and  one  having  a  white  cob  and  a  red  pericarp,  the 
colors  show  spurious  allelomorphism.  The  spurious  allelo- 
morphism is  shown  by  the  F2  generation,  in  which  is  produced  1 
red  pericarp-white  cob  :  2  red  pericarp-red  cob  :  1  white  pericarp- 
red  cob.  His  idea  is  that  in  the  case  first  mentioned  the  colors 
are  both  carried  in  the  same  chromosome  while  in  the  second 
case  they  are  carried  in  different  but  homologous  chromosomes. 
As  Emerson  himself  has  stated,  this  theory  assumes  the  inevi- 
table pairing  of  the  two  chromosomes  carrying  the  colors,  which 
is  probable  but  unproved.  Our  own  data  show  no  facts  diamet- 
rically opposed  to  this  hypothesis  but  the  criticism  regarding 
genes  held  by  different  chromosomes  that  was  made  above  would 
also  apply  here. 

Physical  Transformations  of  Starchiness. 

Although  presence  and  absence  of  starchiness  behaves  as  a 
Mendelian  allelomorphic  pair  in  heredity,  the  physical  condition 
of  the  starch  is  a  different  matter.  Starchiness  acts  as  a  filial 
or  endosperm  character  and  shows  as  Xenia  in  individual  seeds. 


At  meeting  of  Amer.  Soc.  Nat.,  Ithaca,  N.  Y.,  Dec.  29,  1910. 


PHYSICAL  FORM  OF  STARCHY  CHARACTER.     in 

The  physical  condition  of  the  starch  behaves  as  a  plant  character 
affecting  the  entire  ear.  One  may  have  ears  which  show  a 
tendency  towards  the  dented  character  in  some  seeds  and  a 
tendency  towards  the  flint  character  in  other  seeds.  Such  ears 
are  probably  always  heterozygous  dent -flint  combinations,  and 
simply  show  zygotic  variations.  The  different  kinds  of  seeds 
give  the  same  results  in  the  next  generation  and  show  no  tendency 
toward  a  real  segregation  of  dent  and  flint  characters  in  the 
individual  seeds.  . 

The  difference  in  the  appearance  of  the  starch  in  the  different 
races  of  maize  has  been  described  earlier  in  this  paper.  The 
immediate  cause  of  these  differences  is  the  amount  and  location 
of  the  soft  starch  formed  in  proportion  to  that  of  corneous 
or  translucent  starch.  In  the  pop  corns  there  is  total  absence  of 
soft  starch  or  at  most  only  a  small  amount  immediately  sur- 
rounding the  top  and  back  of  the  embryo.  As  this  amount  of 
soft  starch  increases,  the  starch  cells  of  the  seeds  lose  their 
ability  to  hold  the  steam  formed  by  the  moisture  they  contain 
when  heated,  and  can  no  longer  evert  their  entire  contents  as 
cooked  starch.  They  may  pop  slightly  but  they  can  no  longer 
be  considered  commercial  pop  corns.  They  have  passed  into 
the  flint  corn  class.  This  class  includes  varieties  with  varying 
amounts  of  soft  starch  up  to  those  in  which  it  covers  the  cap. 
The  latter  are  dent  corns,  for  the  dent  is  simply  formed  by  the 
greater  percentage  of  contraction  which  the  soft  starch  under- 
goes in  drying.  The  amount  of  dentness  is  in  direct  proportion 
to  the  thickness  of  the  soft  starchy  layer  at  the  cap.  A  few 
varieties  are  known  in  which  the  soft  starch  has  replaced  almost 
all  the  corneous  starch.  They  are  known  as  semi-starchy  corns. 
They  are  not  so  well  known  however,  as  the  floury  corns  in 
which  the  corneous  starch  is  absent. 

As  all  of  these  varieties  are  known  in  Z.  mays  curagua,  Z.  mays 
hirta  and  Z.  mays  tunicata,  it  is  obvious  that  the  proportions 
these  two  kinds  of  starch  (in  appearance  at  least)  plays  a  great 
part  in  the  commercial  classification  of  maize.  Also,  since  so 
many  varieties  are  known  in  which  every  possible  ratio  of  corne- 
ous starch  to  soft  starch  occurs,  it  is  evident  that  the  trans- 
missible characters  which  cause  these  differences  are  relatively 
numerous  and  their  interactions  complex.  For  these  reasons, 
it  is  perhaps  too  much  to  expect  that  the  inheritance  of  this 


112  INHERITANCE  IN  MAIZE. 

complex  of  characters  will  be  cleared  up  until  all  possible  com- 
binations of  these  varieties  have  been  made  and  studied.  Our 
data  serve  only  to  establish  certain  general  facts. 

The  first  bit  of  evidence  in  the  matter  comes  from  a  con- 
sideration of  the  behavior  of  the  only  class  of  maize  varieties  that 
apparently  are  beyond  the  scope  of  the  subject  in  hand  —  the 
sugar  varieties.  When  the  latter  are  crossed  with  starchy 
varieties  it  is  perfectly  clear  that  starchiness  is  a  separate 
character  independent  of  the  physical  form  in  which  it  exists. 
Sugar  varieties  are  found  that  are  simply  dents  and  flints 
which  lack  starchiness.  We  have  also  produced  by  crossing, 
sugar  varieties  that -are  characteristic  pop  corns  lacking  starch. 
No  sugar  varieties  are  known  which  would  be  soft  starch  varie- 
ties (Z.  mays  amylacea)  if  they  contained  the  S  factor,  but  it 
can  hardly  be  doubted  that  such  could  be  produced.  The 
experimental  evidence  is  as  follows.  When  Black  Mexican, 
Early  Crosby  and  Golden  Bantam  are  crossed  with  dent  varie- 
ties, the  Xenia  starchy  seeds,  or  Fi  generation  are  all  flint-like 
in  character.  These  when  grown  produce  Fi  ears  which  have 
an  appearance  intermediate  between  dents  and  flints  and  give 
in  F2  ears  which  are  characteristically  flint  in  character.  In 
the  case  of  the  cross  between  Black  Mexican  sugar  No.  54  and 
Illinois  High  Protein  dent  No.  8,  these  flint  segregates  of  F2 
were  carried  to  the  F3  generation  and  bred  true.  Since  pure 
dent  varieties  were  the  male  parents  of  these  crosses,  the  occur- 
rence of  flints  in  F2  can  only  be  accounted  for  by  supposing  that 
the  sugar  varieties  that  were  used  as  the  female  parents  of 
the  crosses  were  latent  flints.  In  the  same  way  Stowell's  Ever- 
green sugar  and  Late  Egyptian  sugar  were  proved  to  be  latent 
dents  by  crossing  them  with  starchy  flint  varieties.  The  Xenia 
seeds  were  dented  and  pure  dents  appeared  in  the  F2  generation. 
One  peculiar  thing  occurred  in  the  cross  between  Black  Mexican, 
sugar.  No.  54  and  Illinois  High  Protein  dent,  No.  8.  In  Fi  all 
of  the  ears  were  intermediate  between  dent  and  fiint  with  a 
tendency  toward  dentness,  except  one.  This  ear  was  a  pure 
flint  in  appearance.  Only  one  of  the  intermediate  ears  was 
grown  in  the  F2  generation  and  it  produced  91  dents  and  inter- 
mediates and  6  flints.  The  pure  dents  could  not  be  separated 
from  the  intermediates  but  flints  occurred  in  the  ratio  of  one 
out  of  sixteen.     The  ear  which  was  apparently  flint  in  Fi  proved 


PLATE    XVI. 


■H 


sS^ 


At  left,  No.  15,  Longfellow  flint.  At  right,  No.  8  Illinois  high  protein 
dent.  In  center,  Fi  ears  of  cross  15x8,  showing  interinediate  char- 
acter of  physical  condition  in  which  the  starch  is  stored. 


Dent-Flint  Crosses. 


PHYSICAL    FORM    OF    STARCHY    CHARACTER.  113 

to  be  an  intermediate  in  F2.  Thirty-four  ears  were  obtained, 
of  which  three  were  clearly  dented,  a  number  were  intermediate, 
while  from  ten  to  twenty  would  ordinarily  be  classed  as  flints. 
Thirteen  of  the  latter  were  grown  in  the  F3  generation  and 
produced  from  50  to  175  ears  apiece.  Nine  out  of  the  thirteen 
gave  only  flint  ears  in  a  total  of  947  individuals.  The  other  four 
ears  produced  a  total  of  264  ears  of  which  between  10  and  20 
were  flints  (i.  e.  ten  were  certainly  flints  and  ten  others  were 
questionable).  Therefore,  since  9  out  of  13  of  the  20  ears 
classified  as  "probable  flints"  in  F2  proved  to  be  true  flints  in 
F3,  we  have  14  ears  pure  flint  to  20  dents  and  intermediates  in  F2. 
We  do  not  know  enough  about  this  cross  to  say  just  what  occur- 
red here,  but  it  is  probable  that  one  factor  for  dentness  was  miss- 
ing in  the  pollen  which  produced  the  hybrid  seed  from  which 
this  lot  F2  ears  came.  In  the  other  case  a  di-hybrid  ratio 
appears. 

Several  other  crosses  were  made  between  true  dent  and  true 
flint  races,  that  is,  races  in  which  the  parents  both  were  starchy. 
No.  15  Longfellow  flint  was  crossed  with  No.  8  Illinois  High 
Protein  dent.  The  Fi  generation  was  intermediate  in  character. 
Through  an  unfortunate  oversight  data  regarding  the  segrega- 
tion in  F2  were  taken  on  the  progeny  of  only  one  ear  of  the 
three  Fi  ears  planted.  This  ear  gave  33  dents  and  intermediates 
to  3  flints.  About  200  ears  were  obtained  from  the  other 
two  Fi  ears  planted  and  from  our  general  fleld  notes  we  can 
say  that  not  less  than  15  dents  and  intermediates  to  each  flint 
ear  were  obtained.  One  flint  ear  gave  a  crop  of  94  ears  in  F3, 
all  of  which  were  flint.  One  dent  ear  grown  in  F3  also  proved 
to  be  pure.  A  better  idea  of  these  results  is  given  by  the  photo- 
graphs on  Plates  XVI  and  XVII,  however,  than  can  be  given  by 
written  description. 

Two  crosses  were  made  between  No.  11,  Sturgis'  flint  and 
No.  8,  Illinois  High  Protein  dent.  Both  were  intermediate  in 
Fi.  In  F2,  progeny  of  one  Fi  ear  of  the  first  cross  gave  44  dents 
and  intermediates  to  3  flints.  In  F3,  one  ear  from  an  inter- 
mediate of  F2  gave  23  dents  and  intermediates  and  2  flints. 
Five  Fi  ears  of  the  other  cross  were  grown  in  F2  resulting  in 
175  dent  and  intermediate  ears,  and  17  flint  ears.  The  ratio 
here  is  about  10  :  1,  but  if  any  error  was  made  in  the  classifica- 
tion it  certainly  occurred  by  placing  intermediates  in  the  flint 
class. 


114  INHERITANCE  IN  MAIZE. 

Another  cross  of  this  kind  was  that  of  No.  5-5,  Watson's 
fiint  with  No.  2,  Illinois  Low  Protein.  The  ears  were  inter- 
mediate in  Fi.  In  Fo  there  was  segregation,  for  ears  exactly 
like  No.  2  were  obtained.  Out  of  the  101  ears  obtained,  how- 
ever, no  ears  were  produced  that  could  be  classed  definitely 
as  flints.  One  or  two  flint-like  ears  occurred  which  will  be  tested 
for  purity  this  coming  season.  It  is  quite  likely  that  we  have 
here  a  tri-hybrid  or  possibly  a  tetra-hybrid. 

The  female  parent  of  this  cross.  No.  5,  was  also  crossed  with 
No.  6,  Learning  dent.  Fi  generation  was  intermediate  as  before. 
Five  Fi  ears  were  grown  with  the  following  results: 


Dents  and  Inter. 

Flints 

98 

16 

71 

17 

51 

5 

42 

7 

Total,  262 

45 

These  ears  gave  different  ratios.  Probably  more  ears  were 
classed  as  flints  than  would  prove  to  be  such  in  the  Fa  generation, 
yet  they  were  classified  similarly  in  each  case  and  Fs  tests 
would  probably  only  reduce  the  proportion  of  flints  from  each 
ear.  Paradoxical  as  it  may  seem,  however,  different  ratios 
are  to  be  expected  in  F2  if  the  general  hypothesis  concerning 
the  applicability  of  Mendelian  principles  to  cases  where  varia- 
tion is  apparently  continuous,  is  true  (East  :  10).  This  is 
explained  in  the  following  paragraphs. 

In  the  crosses  described  above  three  facts  stand  out  definitely. 
The  characters  which  give  the  flint  or  the  dent  appearance  to 
maize  are  transmitted  as  plant  characters  to  the  entire  ear  and 
not  as  endosperm  characters  to  the  individual  seed.  They 
conform  to  the  essential  feature  of  Mendelism  by  showing 
segregation;  and  they,  are  due  to  the  action  of  more  than  one 
transmissible  character.  The  question  remains,  can  any  or  all 
of  these  characters  be  named  ? 

Our  experience  suggests  that  the  proportion  of  corneous 
starch  to  soft  starch  depends  partially  upon  size  and  shape  of 
the  pericarp  and  upon  the  number  of  rows  per  ear.     All  of  the 


PHYSICAL    FORM    OF    STARCHY    CHARACTER.  115 

races  (pop  corns)  in  which  soft  starch  is  absent  have  small  seeds, 
and  the  full  corneous  starch  character  cannot  be  transferred  to 
large  seeds  by  recombination  through  hybridization.  On  the 
other  hand,  by  crossing  a  pop  maize  with  a  dent  maize  dent 
seeds  may  be  obtained  which  are  much  smaller  than  many  races 
with  flint  seeds.  Further,  dent  races  are  known  which  have 
much  larger  seeds  than  some  races  in  which  the  corneous  starch 
is  entirely  absent  (the  flour  corns).  There  is  also  some  rela- 
tion between  the  size  of  the  plant  and  the  amount  of  soft  starch 
in  their  seeds.  The  floury  or  semi-floury  corns  are  in  general 
larger  than  the  corneous  starchy  corns.  Here  again,  however, 
there  is  an  overlapping,  for  we  have  produced  dent  races  by 
crossing  with  dwarf  pop  races,  which  are  much  smaller  in  size 
than  the  large  pop  and  flint  races. 

Relationship  between  the  physical  character  of  the  starch  and 
shape  of  pericarp  is  much  more  intimate  than  it  is  between  the 
former  and  size  characters.  In  the  rice  pops  the  pericarp  is 
drawn  to  a  point  at  the  place  where  the  silk  is  attached.  This 
makes  the  rice  pop  races  have  rather  long  slender  seeds,  but  it 
is  probably  due  to  a  separate  character  or  characters.  Leaving 
this  complication  out  of  consideration  one  may  say  that  the 
pop  corns  have  small  seeds  which  are  almost  as  broad  as  they 
are  long.  As  the  seeds  become  larger,  if  the  ratio  of  length  to 
breadth  remains  about  unity  or  less,  flint  races  are  formed. 
If,  instead,  the  ratio  of  length  to  breadth  increases,  dent  races 
are  formed.  On  the  other  hand,  medium  large  to  large  seeded 
races  may  have  almost  any  ratio  of  length  to  breadth  and  be 
either  flint,  dent  or  floury  varieties. 

Of  course  the  shape  of  the  pericarp  depends  somewhat  on  the 
number  of  rows,  as  the  greater  this  number  the  more  the  seeds 
are  crowded  together  and  thus  lengthened.  Small-seeded  pop 
and  flint  races  exist  with  as  high  as  20  rows,  but  when  the  seeds 
are  medium  in  size  flint  races  are  usually  8-rowed  and  12-rowed, 
and  never  —  in  our  experience  —  over  16  rowed.  Dent  races, 
on  the  other  hand,  seldom  occur  with  less  than  12  rows,  but 
when  large  seeded  they  do  exist  with  as  few  as  eight  rows. 
Floury  races  we  have  never  seen  with  less  than  10  rows,  but 
they  reach  as  high  as  24  rows. 

These  relationships  may  simply  be  correlations  and  not 
direct  causes  of  the  proportion  of  corneous  starch  to  soft  starch 


ii6  INHERITANCE  IN  MAIZE. 

that  exists  in  various  strains  of  corn.  But  even  if  the\^  were 
directly  concerned,  they  could  not  account  for  the  large  number 
of  differences  in  varieties,  for  none  of  the  correlations  are  suf- 
ficiently high.  Many  other  characters,  the  exact  nature  of 
which  is  unknown,  must  be  concerned  in  the  matter.  The 
simplest  interpretation  of  the  matter  seems  to  be  the  interaction 
of  independent  allalomorphic  pairs  of  the  nature  reported  by 
Nillson-Ehle  (:  10)  and  East  (:  10)  in  earlier  papers.  If  this 
interpretation  be  granted,  one  should  expect  that  greatest 
difference  in  character  pairs  would  exist  in  the  case  of  pop  and 
starchy  races.  Flint  and  dent  races  with  about  the  same  size 
seeds  and  small  differences  in  number  of  rows  should  differ 
by  fewer  pairs  of  characters. 

We  have  seen  that  in  two  of  such  crosses  the  evidence  points 
to  the  existence  of  two  allelomorphic  pairs  giving  pure  flints  and 
pure  dents  in  the  F2  generation  once  in  every  sixteen  individuals. 
In  another  cross  (5-5  x  2)  at  least  three  character  pairs  are  con- 
cerned. It  happened  that  in  two  of  these  cases  the  male  parents 
were  Illinois  High  Protein  and  Illinois  Low  Protein  dent  races, 
which  gives  us  some  idea  as  to  why  there  was  a  di-hybrid  ratio 
in  one  case  and  a  higher  ratio  in  the  other  case.  These  two 
strains  were  both  isolated  by  selection  from  a  commercial 
variety  known  as  Burr's  White.  This  variety,  as  are  most 
commercial  varieties,  is  a  mixture  of  complex  hybrids.  By  con- 
tinued selection  of  ears  high  in  protein  and  of  ears  low  in  protein 
with  close  interbreeding  of  the  progeny  these  two  strains  were 
isolated.  The  high  proteid  race  is  characterized  by  a  high 
percentage  of  corneous  starch,  bringing  it  into  closer  relationship 
to  the  flint  corns.  The  low  proteid  race  is  characterized  by 
a  high  percentage  of  soft  starch,  bringing  it  into  closer  relation- 
ship with  the  flour  corns.  It  was  the  high  proteid  strain,  that 
is,  the  one  nearer  the  flint  varieties,  that  gave  the  di-hybrid 
ratio  when  crossed  with  a  flint  race;  while  the  low  proteid 
strain,  —  the  one  nearer  the  flour  corns,  —  gave  the  higher 
ratio. 

This  result  is  what  one  should  expect,  but  can  the  6  :  1 
ratio  obtained  in  the  cross  between  No.  5  and  No.  6  be  explained 
so  easily?  We  believe  it  presents  no  difficulties  if  the  complex 
gametic  constitution  of  No.  6  is  properly  appreciated.  The 
individual  which  furnished  the  No.  6  pollen  came  from  a  selfed 


SIZE   CHARACTERS.  117 

daughter  ear  of  the  original  No.  6.  Its  sister  ears  varied  in 
number  of  rows  from  12  to  20  with  the  mode  at  16.  The 
individual  furnishing  the  pollen  in  cross  5x6  was  in  all  prob- 
ability therefore  a  complex  hybrid  itself,  and  the  cross  instead 
of  being  simple  was  really  a  collection  of  crosses.  There  is 
no  doubt  that  many  intermediate  ears  were  classed  as  flint 
in  the  table  given  above.  If  they  could  all  be  grown  for  another 
generation  it  is  quite  likely  that  a  series  of  mono-di-tri  and 
higher  hybrids  would  be  found.  It  may  be  asked  why,  if  this 
is  the  case,  were  not  the  other  crosses  complex?  The  answer 
is  that  they  undoubtedly  were  more  complex  than  they  seemed. 
For  example,  if  a  large  number  of  Fi  ears  were  grown  it  is  likely 
that  some  would  give  ratios  other  than  those  found.  It  was 
simply  chance  that  gave  us  fairly  good  di-hybrid  ratios  from 
a  few  Fi  ears  in  two  instances.  The  most  important  reason 
why  the  cross  with  No.  6  was  likely  to  be  more  variable  than 
the  others,  however,  lies  in  the  fact  that  all  of  the  other  strains 
had  been  inbred  for  much  longer  periods. 


Size  Characters. 

The  remainder  of  Part  IV  will  be  devoted  to  a  discussion  of 
the  inheritance  of  size  characters,  —  variations  that  have  been 
considered  to  be  and  to  casual  observation  are,  continuous. 
Our  studies  have  been  concerned  with  the  number  of  rows  per 
ear,  height  of  plant,  length  of  ear  and  size  of  seed. 

It  is  perfectly  obvious  to  one  familiar  with  the  maize  plant 
that  it  is  almost  impossible  to  work  out  in  detail  the  inheritance 
of  the  complex  factors  that  interact  to  cause  the  transmissible 
differences  in  the  size  of  its  organs.  That  size  characters  are 
complex  in  themselves  is  shown  by  the  numerous  varieties 
grown  commercially.  They  each  vary  from  their  own  means, 
but  different  variety  means  in  height  are  found  all  the  way 
from  two  and  one-half  to  fourteen  feet  with  but  little  actual 
difference  between  the  most  similar  strains.  Further  to  com- 
plicate matters,  all  size  characters  respond  to  environmental 
stimuli,  and  these  non-inherited  fluctuations  obscure  the 
analysis  of  pedigree  cultures  in  a  still  greater  degree.  For 
these  reasons  we  do  not  attempt  to    analyze    our  results  further 


ii8 


INHERITANCE  IN  MAIZE. 


than  to  say  that  they  do  show  segregation  in  every  case*  And 
segregation  is  held  to  he  the  important  and  essential  feature  of 
Mendelism.  Therefore  we  believe  that  size  characters  mendelize. 
Let  us  now  consider  the  hypothesis  by  which  segregation  in 
characters  apparently  continuous  in  their  variation,  could  come 
about.  Nillson-Ehle  (:  09)  has  shown  that  black  glumes  in  oats 
when  crossed  with  their  absence  behave  sometimes  as  mono- 
hybrids  and  sometimes  as  di-hybrids,  and  that  presence  and 
absence  of  red  pericarp  color  in  wheat  sometim.es  behaves  as  a 
tri-hybrid.  He  further  showed,  although  not  quite  so  con- 
clusively, that  presence  and  absence  of  ligule  in  oats  behaves 
as  a  tetra-hybrid.  In  this  and  in  a  former  paper  (East  :  10) 
it  has  been  shown  that  yellow  endosperm,  red  pericarp  and 


TABLE  26. 

INHERITANCE    OF    ROWS   IN    CROSS    (5  X  6). 


No. 

Gen. 

Rows 

of 

Parents 

Row  Classes 

8    •   10 

12 

14 

16 

18 

20 

22 

24 

No.  5  flint 
(2  yrs.) 
No.  6  dent 
No.  5  X  6 
(5  X  6)-l 
(5  X  6)-2 
(5  X  6)-22 
(5  X  6)-23 

P 
P 

F2 

F2 
F2 

8 

18 
8 
12 
10 
10 
12 

289 

13 
12 

7 
8 
4 

2 

36 

48 
22 
45 
25 

2 

6 
53 
35 
15 
31 
60 

31 
10 

9 
2 

1 

18 

51 

1 

4 

18 
2 

4 
1 

dented  seeds  (as  opposed  to  flinty  seeds)  behave  as  di-hybrids, 
with  so  many  data  that  the  facts  can  hardly  be  questioned. 
We  have  also  shown  although  less  conclusively  that  other  red 
pericarped  varieties  and  other  varieties  which  differ  in  their 
ratios  of  soft  to  corneous  starch  behave  as  higher  hybrids. 

It  should  be  clearly  understood  what  this  means  to  Mendelian 
theory.  Several  genes  for  the  same  character  may  exist  in  the 
germ  cells  of  one  organism,  the  number  being  limited  possibly  by 
the  number  of  chromosomes.     The  limited  number  of  cases  thus 


*  It  is  probable  that  the  number   of  internodes  per  plant  is  one  of  the 
factors  directly  concerned  in  the  inheritance  of  height  of  plant. 


PLATE    XVII. 


a.     F2  dent  segregate  above   (frequency  about  i  in  10).     Random  sample 
of  its  F3  progenj'  below. 


-    -A 


^-vS^ 


.Vf'  i 


b.     F2  flint   segregate  above    (frequency  about   i   in   16).     Random  sample 
of  its  F3  progeny  below. 

Dent-Flint  Crosses. 


SIZE   CHARACTERS. 


ug 


far  found  presumably  is  due  to  the  fact  that  few  size  characters 
have  been  investigated,  for  nowhere  would  these  phenomena  be 
so  likely  to  occur  as  in  quantitative  characters. 

It  is  fortunate  for  us  that  it  has  been  possible  to  prove  the 
presence  of  several  independent  allelomorphic  pairs  due  to 
produce  the  same  somatic  character,  for  characters  like  color 
where  dominance  is  relatively  perfect.  Beginning  with  this 
as  a  basis,  one  can  extend  the  theoretical  possibilities  of  such 
facts  to  other  cases  and  thus  be  better  prepared  for  the  paradox- 
ical complexities  that  occur  in  actual  pedigree  cultures.  When 
in  a  cross  there  is  simple  presence  dominant  to  absence  of  one 
gene  for  a  certain  character,  the  ratio  in  F2  is  3  dominant  to 
1  recessive ;  when  two  independent  allelomorphic  pairs  producing 
the  same  character  are  concerned,  the  ratio  in  F2is  15  dominants 

TABLE  27. 

INHERITANCE    OF    ROWS    IN   CROSS      (5    X  2). 


No. 

Gen. 

Rows 

of 

Parents 

Row  Classes 

8 

10 

12      14 

16 

18 

20 

22 

24 

No.  5  flint 

(2  yrs.)     ^ 
No.  2  dent 
No.  5  X  2 
(5  X  2)-6 

P 

P 

Fi 
F2 

8 

16 

8 

10 

289 

i 

4 

2 
'9 

18 

2 

2      14 
20  1     4 
61      14 

56 
3 

42 
1 

20 

1 

1 

to  1  recessive.  In  general  then  if  n  allelomorphic  pairs  are 
concerned,  in  F2  there  will  be  a  ratio  of  4''-!  dominants  to  1 
recessive.  It  is  not  likely  however  that  dominance  is  ever 
perfect  in  these  complex  hybrids.  For  example,  in  the  case  of 
the  two  yellow  colors  in  the  maize  endosperm,  the  intensity  of 
the  yellow  decreases  in  the  following  order  Y1Y1Y2Y2,  Yiyi 
Y2Y2  or  YiYiY2y2,  YiYi  or  Y2Y2,  Yiyi  or  Y2y2  and  yiyiy2y2. 
In  size  characters  dominance  is  probably  very  incomplete  or 
absent.  A  heterozygous  combination  presumably  produces 
half  the  effect  of  a  homozygous  combination.  Then  as  domi- 
nance becomes  less  and  less  evident  the  Mendelian  classes  vary 
more  and  more  from  the  formula  (3  +  1)"  and  approach  the 
normal  curve  of  error  (3^  +  3^)."     When  there  is  no  dominance 


I20  INHERITANCE  IN  MAIZE. 

and  open  fertilization,  a  state  is  reached  in  which  the  curve  of 
variation  simulates  the  fluctuation  curve,  with  the  difference 
that  the  gradations  are  heritable.  The  heritable  variations 
are  always  more  or  less  obscured,  however,  by  the  ever  present 
fluctuation. 

The  experimental  results  may  now  be  considered — remembering 
only  that  fluctuations  are  present  and  that  in  maize  many 
genotypes  are  often  present  in  one  parent.  In  Table  26  are 
shown  the  results  from  a  cross  between  a  race  practically  pure 
to  the  eight  rowed  type.  No.  5,  and  a  dent  No.  6,  which  varies 
from  twelve  to  twenty  rows  with  the  mode  at  sixteen  rows.  The 
Fi  generation  is  intermediate  and  furnished  four  inbred  ears 
that  were  grown  in  the  F2  generation.  Now  three  of  these 
four  F2  families  show  no  greater  range  of  variation  than  Fi, 


TABLE  28. 

INHERITANCE   OF   ROWS   IN   CROSS    (11x5). 


No. 

Gen. 

Rows 

of 

Parents 

Row  Classes 

8 

10 

12 

14 

16 

18 

20 

22 

24 

No.  11  flint 
No.  5  flint 
No.  11  X  5 
(11  X  5)-8 
(11  X  5)-18 

P 
P 

Fi 
F2 
F2 

12 
8 
12 
12 
10 

1 

289 

2 

10 

19 

4 

2 
11^ 
38 
33 

387 

2 

26 

107 

100 

7 

2 

23 

5 

1 

8 

yet  it  is  a  noticeable  fact  that  they  vary  in  different  ways.  Ear 
(5  X  6)-l  shows  a  modal  condition  at  ten  rows.  It  may  be 
considered  that  the  crossed  seed  from  which  the  Fi  ear  that 
produced  this  crop  came,  contained  the  genes  for  lower  numbers 
of  rows  from  the  varying  parent.  No.  6.  Ear  (5  x  6)-23,  on  the 
other  hand,  evidently  contains  genes  from  No.  6  that  were  due 
to  produce  higher  numbers  of  rows. 

Table  27  shows  a  slightly  higher  variability  in  F2  than  in 
Fi. 

Table  28  is  interesting  because  it  shows  the  results  of  a  cross 
between  two  varieties  that  have  been  selected  for  many  years 
until  they  are  relatively  true  to  the   12-rowed  and  8-rowed 


PLATE   XVIII. 


a.     No.  60,  Tom  Thumb  maize,  showing  variation  in  length  of  ear.    Class 
centers  are  even  centimeters  {}q). 


/»j^/     /3        14       /s      J6      n  n       n  20      I) 

Ky.^       3  n       n       ts       W  rf      10  i       1 

b.     No.   54.  Black  Mexican   sugar  maize,  showing  variation   in   length   of 
ear  {}{). 


Inheritance  of  Length  of  Ear. 


PLATE    XIX. 


Length        7 


16  17  18  19 


11      11       H       n 


Variation  in  length  of  ear  of  Fi,  generation  of  cross  between  No.  60 
and   No.  54  (ig). 


^         '^         10         n         12  1^         14         15         10        J7  lb        19 

-V,.  K.,     f        s      II      S(.       do       ns      izf      7;        q       n       n       i>        1 

b.     Variation  in  length  of  ear  of  F2  generation  of  cross  between  No.  60 
and  No.  54.     Family   (60-5x54)    CY). 


Inheritance  of  Length   of   Ears. 


PLATE     XX. 


a.     Variation  in  length  of  ear  of  F2  generation  of  cross  between  No.  60 
and  No.  54.     Family   (60-3x54)    (i,;)- 


7 

8 

9 

10 

11 

12 

13 

14 

15 

IG 

17 

18 

0 

20 

2) 

2 

5 

n 

33 

53 

33 

n 

It 

13 

10 

II 

\i 

1 

^ 

/ 

b.     Variation  in  length  of  ear  of  ¥2  generation  of  cross  between  No.  60 
and  No.  54.     Family   (60-8x54)   {}'^). 


Inheritance  of  Length   of   Ears. 


PLATE    XXI. 


^ 


V 


K 


^%  ^% 


K 


^WQ9^^ 


r. 


'^€^' 


a.  Average  size  of  seeds  of  No.  60  (upper  left)  and  No.  54  (lower  left) 
and  the  Fi  generation  of  the  cross  between  them.  E.xtremes  of  the 
F2  generation  at  right. 


>r 


h.     Average  ears  of  No.  60  (left)  and  No.  58  (right)  with  average  of  Fi 
generation  in  center.     Extremes  of  F2  generation  shown. 


Size  Inheritance. 


SIZE   CHARACTERS. 


121 


TABLE  29. 

INHERITANCE   OF   ROWS   IN   CROSS    (11  X  18). 


No. 

Gen. 

Rows 

of 

Parents 

Row  Classes 

8 

1 
13 

2 
1 
8 

10 

12 

14 

16 

18 

20 

22 

24 

No.  11  flint 
No.  18  sugar 

(2  yrs.) 
No.  11  xl8 
(11  X  18)-4 
(11  X  1S)-10 

P 
P 

Fi 

F2 
F2 

12 

12 

12 
12 
10 

10 

9 

13 

387 
51 

24 

78 
62 

7 
4 

1 
10 
13 

1 
1 

conditions,  respectively.  F2  shows  a  distinctly  higher  varia- 
bility than  Fi.  It  is  expected  that  8-rowed  F2  plants  may 
breed  relatively  true. 

Table  29  is  given  simply  to  show  that  a  cross  between  two 
12-rowed  varieties  does  not  show  an  extension  of  the  row  classes. 
Such  a  condition  should  sometimes  be  possible  if  our  general 
hypothesis  is  true,  yet  it  might  not  occur  in  more  than  one  cross 
in  hundreds. 

Table  30  shows  the  results  from  a  cross  between  another  variety 
true  to  the  eight  rowed  condition  and  a  variety  which  varies  from 
ten  to  eighteen  rows  with  the  modal  condition  at  twelve.  Un- 
fortunately only  a  few  plants  matured  in  the  Fi  generation  and 
no  conclusions  can  be  drawn  regarding  its  variability.  The  F2 
generation    apparently    shows    a     marked    segregation.     The 


TABLE  30. 

INHERITANCE   OF   ROWS   IN   CROSS    (15  X 


Rows 

Row  Classes 

No. 

Gen. 

of 
Parents 

8 
100 

10 

12 

14 

16 

18 

20 

22 

24 

No.  15  flint 

P 

8 

1 

No.  8  dent 

P 

14 

3 

54 

36 

12 

2 

No.  15  X  18 

F, 

8 

2 

5 

(15  X  8)-2 

F, 

10 

14 

15 

28 

9 

1 

(15  X  8)-3 

Fo 

12 

4 

13 

25 

6 

3 

(15  X  8)-2-10 

F, 

14 

1 

8 

14 

6 

1 

1 

(15  X  8)-2-l 

:   F, 

8 

32 

35 

23 

4 

(15x  8)-2-5 

1 

Fs 

12 

4 

.  41 

116 

15 

3 

1 

122  INHERITANCE  IN  MAIZE. 

results  in  the  Fs  generation  are  the  most  interesting,  however, 
for  the  progeny  of  an  eight  rowed  F2  show  a  distinct  tendency 
toward  an  8-rowed  condition,  while  progeny  of  F2  ears  having 
twelve  and  fourteen  rows  respectively,  though  highly  variable, 
show  a  transmission  of  their  parental  qualities. 

Our  largest  pedigree  series  for  number  of  rows  is  shown  in 
Table  31.  The  male  parent  is  the  same  as  was  used  in  the 
previous  cross.  The  female  parent  is  an  eight-rowed  type  but  is 
not  so  pure  for  this  condition  as  the  eight-rowed  varieties  prev- 
iously used.     The  general  crop  in  Fi  was  discarded  before  the 


TABLE  31. 

INHERITANCE   OF   ROWS   IN   CROSS    (8x54). 


Rows 

Row  Classes 

No. 

Gen. 

of 
Parents 

8 

10 

12 

14 

16 

18 

20 

22 

24 

No.  8  dent 

P 

12 

3 

54 

36 

12 

2 

No.  54  sugar 

P 

8 

89 

25 

7 

No.  8  X  54 

El 

12 

1 

6 

14 

(8  X  54)-l 

F, 

12 

9 

22 

16 

1 

(     "     )-5 

F, 

12 

1 

3 

16 

1 

(     "      )-!-! 

F,, 

10 

15 

87 

4 

(      "      )-l-2 

F,, 

8 

20 

38 

50 

(     "     )-l-2a 

F,, 

10 

61 

48 

54 

(     "     )-l-3 

F,, 

10 

32 

75 

15 

(     "     )-l-3a 

F, 

8 

5 

20 

27 

1 

(     "      )-l-5 

F,, 

12 

33 

158 

26 

3 

(     "     )-l-6 

F, 

12 

4 

36 

109 

8 

2 

(     "     )-l-10 

Fa 

8 

Very  irre 

gular 

,  mostly  8-rowed 

(     "     )-l-13 

Fa 

10 

96 

43 

8 

data  was  taken  upon  the  number  of  rows.  This  oversight  is 
partially  rectified  by  the  records  from  21  hand-pollinated  ears, 
but  the  true  variability  is  presumably  somewhat  greater.  Two 
Fi  ears  were  grown  in  the  F2  generation,  one  having  the  moda 
condition  at  ten  rows  and  the  other  at  twelve  rows.  Nine  ears 
from  the  Fj  progeny  from  (8  x  54)-l  produced  Fa  crops.  This 
table  should  be  examined  in  order  to  appreciate  the  significance 
of  the  results  of  this  generation.  There  is  a  marked  tendency 
in  different  ears  to  segregate  into  twelve-row  and  eight-row 
types.     Two  of  the  ears  have  modal  conditions  at  ten  rows. 


SIZE   CHARACTERS.  123 

but  their  variability  is  so  great  that  the  presumption  is  that 
this  represents  simply  the  continuance  of  the  heterozygous 
condition.  In  our  opinion  there  is  no  question  about  segre- 
gation of  number  of  rows  but  we  are  perfectly  aware  that  the 
believer  in  selection  would  be  justified  in  the  criticism  that  that 
is  the  cause  of  the  results  obtained. 

Table  32  shows  the  frequency  distribution  of  the  heights  of 
two  varieties  Nos.  5  and  6,  and  the  Fi  and  F2  generations  of  the 
resulting  cross.  A  good  idea  of  the  possible  segregation  in  the 
F2  generation  of  such  crosses  as  this,  is  obtained  by  the  compara- 
tive size  of  the  coefficient  of  variation  of  the  Fi  and  the  F2 
generations.  In  eveyy  case  it  is  at  least  50%  higher  in  the  Fj 
generation  than  in  the  Fi  generation.  The  Fi  generation  is 
not  intermediate  between  the  two  parents  but  is  nearly  as  high 
as  the  taller  parent.  This  fact  is  not  to  be  regarded  as  in  any 
way  connected  with  dominance.  It  is  due  to  the  increased 
vigor  which  comes  from  crossing  in  maize  as  shown  in  a  previous 
paper  (East  :  09) .  The  total  results  of  the  F2  generations 
show  segregation  from  the  lowest  class  range  of  the  shorter 
parent  to  the  highest  class  range  of  the  taller  parent.  It  must 
not  be  thought  however  that  these  segregates  are  regarded  as 
pure  types.  Their  behavior  in  further  generations  is  still 
problematical.  Continued  selection  of  shorter  or  taller  segre- 
gates presumably  will  give  an  approach  toward  the  selected 
condition.  The  criticism  that  any  such  results  would  be  due 
to  selection  and  not  segregation  is  not  valid  in  this  case,  however, 
for  segregates  of  extreme  types  that  never  appear  in  either  of 
the  parents  alone  have  occurred  here  in  the  F2  generation. 

Table  33  shows  similar  segregation  in  heights  of  plants  in 
another  cross,  No.  (54x60).  The  frequency  distribution  of 
the  heights  in  No.  54  was  obtained  from  plants  grown  during 
the  season  and  on  the  same  soil  upon  which  the  F2  generation 
was  grown.  The  exact  distribution  of  heights  of  No.  60  and 
of  the  Fi  ears  was  not  taken  because  at  that  time  another 
object  was  in  view.  The  range  of  distribution  as  shown  by 
the  black  lines,  is  correct.  From  notes  recorded  at  the  time 
we  know  that  the  Fi  generation  was  quite  uniform,  the  measure- 
ments being  distributed  around  classes  67  to  73.  Here  again 
the  effect  of  crossing  is  observed  in  the  relatively  tall  plants  of 
this  generation.     The  lowest  plants  in  the  F2  generation  reach 


124  INHERITANCE  IN  MAIZE. 

the  upper  range  of  No.  60  while  the  highest  plants  are  practically 
the  height  of  the  highest  plants  of  No.  54.  The  reason  that 
no  plants  were  obtained  in  the  lower  range  of  No.  60  is  due  no 
doubt  to  their  continued  heterozygous  condition  in  some  of 
their  characters  and  therefore  an  increksed  vigor. 

Table  34  shows  that  the  lengths  of  ears  in  the  above  cross 
segregate  in  a  similar  manner.  The  Fi  generation  is  not  forced 
toward  the  long-eared  parent  as  it  is  in  the  heights  of  the  plants. 
In  other  words  ear  length  does  not  show  the  increased  vigor 
due  to  heterozygosis  that  is  seen  in  the  heights  of  plants.  There 
can  be  scarcely  a  doubt  that  the  greatly  increased  variability 
in  Fi  is  the  direct  .result  of  segregation. 

The  segregations  of  weights  of  seeds  in  the  above  cross  is 
shown  in  Table  35.  The  Black  Mexican  parent  No.  54  shows 
somewhat  distorted  variation  in  this  character  as  there  are 
four  classes  of  large  sized  seeds  containing  only  six  ears  in  all. 
No  F2  segregates  occurred  of  this  size.  The  reason  is  that  the 
ears  of  No.  54  which  produced  this  crop  were  commercial  seed 
of  which  only  three  individuals  were  used  in  crossing.  The 
Fi  generation  in  both  Tables  34  and  35  were  recorded  from  only 
one  cross  although  three  crosses  were  made.  To  be  strictly 
fair,  therefore,  the  F2  generation  of  cross  No.  (60-5  x  54)  is  the  only 
one  that  can  be  directly  compared  with  the  Fi  generation  given. 
We  have  records,  however,  of  a  sufficient  number  of  ears  of  the 
other  two  crosses  to  know  that  they  differ  but  slightly  if  any 
from  the  one  recorded  in  the  tables.  But  even  if  we  should 
be  conservative  and  leave  out  of  consideration  the  Fj  genera- 
tions of  crosses  (60-8  x  54)  and  (60-3  x  54) ,  there  is  still  no 
question  but  that  segregation  has  occurred. 


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PLATE   XXII. 


a.     Fasciated   ears.     F2  generation   of   cross   with   normal   showing  domi- 
nants and  heterozvgotes. 


b.  F2  cob  of  heterozygote  above;  sample  of  F3  progeny  below.  From 
left  to  right  first  six  show  the  abnormality  in  different  degrees.  Last 
two  ears  are  normal. 


Inheritance  of   Ear  Fasciations. 


o, 


DWARF  FORMS.  '  129 


PART  V. 

PLANT    ABNORMALITIES. 

A  few  abnormalities  have  appeared  in  the  maize  varieties 
under  observation  during  the  progress  of  these  investigations. 
They  have  been  studied  with  two  objects  in  view.  The  first 
object  was  to  see  whether  the  manner  of  transmission  of  herit- 
able monstrous  characters  gives  any  clue  to  the  reason  why 
monstrosities  have  seldom  obtained  a  foothold  in  nature  when 
in  competition  with  normal  types.  The  second  object  was 
commercial.  If  teratological  specimens  appear  in  commercial 
varieties  of  maize,  it  is  desirable  to  know  the  easiest  method  to 
destroy  them. 

Dwarf  Forms. 

The  first  dwarf  form  appeared  in  the  1908  culture  of  No.  6 
Leaming  dent.  Thi^  strain  had  been  selfed  for  the  two  previous 
years  without  producing  dwarfs.  In  the  third  generation,  how- 
ever, in  a  culture  of  100  plants  5  dwarfs  appeared.  The  plants 
were  normal  in  appearance,  having  all  parts  correlated  as  in  the 
full  sized  plants,  as  is  shown  in  Plate  XXV.  They  were  from 
two  to  three  feet  in  height  and  contrasted  strangely  with  the 
other  plants  of  the  variety  which  were  from  nine  to  eleven 
feet  in  height.  The  female  flowers  seemed  to  be  normal.  At 
least  cobs  were  formed  and  silks  appeared.  The  pollen  however 
was  completely  sterile.  The  dwarf  plants  were  pollinated 
first  with  their  own  pollen  and  when  no  seeds  formed  were 
pollinated  with  pollen  from  normal-sized  plants.  A  few  seeds 
formed  on  two  ears,  which  were  planted  the  next  season.  From 
one  ear  which  had  been  borne  on  a  plant  eighteen  inches  high 
only  two  plants  resulted,  one  being  a  dwarf  and  the  other 
of  normal  height.  From  the  other  ear  which  came  from  a  plant 
three  feet  six  inches  high,  seventeen  individuals  resulted,  one  of 
which  was  a  dwarf.  The  dwarfs,  as  in  the  former  year,  had  a 
normal  correlation  of  parts.  The  leaves  were  opposite  and  the 
ear  appeared  in  the  axil  of  the  sixth  leaf  from  the  top  as  in  the 


130  INHERITANCE  IN  MAIZE. 

normal  plants.  The  pollen  appeared  to  contain  some  normal 
grains  this  year  and  both  of  the  plants  were  selfed.  No  seed 
set,  however,  and  when  pollinated  with  pollen  from  normal 
plants  it  was  found  that  the  silks  had  passed  the  receptive 
stage.  This  delay  lost  the  strain.  Seeds  from  the  old  ear 
of  No.  6  had  again  been  planted  and  had  given  two  dwarfs  out 
of  sixty  plants,  but  these  had  been  lost  in  the  same  manner. 

No.  69-5  a  flint  with  a  mosaic  red  pericarp  also  gave  similar 
dwarfs  with  a  ratio  of  48  normal  to  14  dwarf  plants.  The  ear 
from  which  they  came  was  a  selfed  ear  from  a  commercial 
strain  obtained  the  year  before.  The  commercial  strain  had 
given  no  dwarfs  but  as  only  about  100  plants  had  been  grown 
it  is  uncertain  whether  or  not  they  had  ever  appeared  before. 

A  different  kind  of  dwarf  plant  appeared  in  a  commercial 
strain  of  Stowell's  Evergreen  sugar  corn  in  1908.  It  was  very 
short  (18  inches)  and  had  short  leaves  of  the  normal  breadth. 
The  joints  were  very  close  together  and  the  whole  appearance 
of  the  plant  suggested  a  normal  plant  that  had  been  pushed 
together  like  a  telescope.  An  attempt  to  self  this  plant  failed, 
but  four  days  afterward  it  was  pollinated  with  pollen  from  a 
normal  strain  of  Stowell's  Evergreen.  A  fairly  good  ear  resulted 
which  was  planted  in  1909.  One  dwarf  like  the  maternal 
parent  appeared  out  of  thirty-seven  plants.  It  was  completely 
sterile,  but  a  selfed  normal  plant  from  the  same  lot  gave  two 
dwarfs  out  of  seventy-six  plants  in  1910.     (See  Plate  XXIV.) 

It  is  a  matter  of  conjecture  what  occurred  in  these  cases.  In 
the  first  instance,  at  least,  controlled  cultures  that  had  produced 
no  dwarf  plants,  suddenly  threw  dwarfs.  It  was  a  much  more 
definite  occurrence  than  De  Vries'  Oenothera  mutations  for 
these  were  mutating  when  De  Vries  found  them.  If  the  normal 
type  were  completely  dominant,  one  must  conclude  that  one 
seed  had  been  selfed  in  the  case  where  the  dwarf  was  pollinated 
with  pollen  from  normal  Stowell's  Evergreen.  In  the  other 
two  cases  the  cross-pollination  was  made  with  pollen  from 
plants  of  the  same  strain,  and  as  only  a  small  number  of  individ- 
uals were  produced  in  the  next  generation,  production  of  dwarfs 
was  probably  continued  through  the  pollen  gametes. 

The  variation  was  transmitted  by  plants  normal  in  character, 
and  whether  one  believes  it  to  be  a  case  of  Mendelian  dominance 
of  normals  or  not,  there  was  nevertheless  definite  segregation. 


REGULARITY  OF  ROWS  OF  SEEDS.  131 

The  fact  that  segregates  appeared  in  ratios  of  less  than  one 
abnormal  to  three  normal,  may  have  been  due  to  any  one  of 
several  causes.  Abnormal  zygotes  may  have  been  formed  and 
not  have  been  able  to  develop,  for  the  germinating  power  of  the 
seeds  formed  on  the  dwarf  plants  was  very  low.  On  the  other 
hand,  it  may  be  that  this  result  was  due  to  the  same  fact  that 
probably  gives  rise  to  higher  ratios  in  crosses  that  have  been 
studied  thoroughly;  namely,  more  than  one  chromosome 
possesses  the  necessary  material  for  normal  height.  There  is 
also  the  possibility  that  many  abnormalities,  particularly  those 
which  show  great  latitude  in  their  development,  are  due  not  to 
regular  Mendelian  segregation,  but  to  some  abnormal  chromo- 
some reduction.  If  some  reductions  took  place  normally  and 
some  abnormally  through  some  disturbance  of  the  plant's 
normal  physiology,  abnormal  and  normal  plants  might  be  pro- 
duced without  definite  and  constant  ratios. 

Regularity  of  Rows  oj  Seeds  on   Cob. 

The  great  majority  of  maize  ears  have  rows  of  seeds  running 
in  straight  regular  rows  from  butt  to  tip.  Sometimes  two  rows 
or  even  four  rows  may  be  dropped  in  going  from  the  butt  to 
the  tip  but  even  then  a  sufficient  amount  of  regularity  exists 
to  call  them  straight-rowed  ears.  A  varying  percentage  of 
ears  in  each  variety,  however,  have  the  rows  quite  irregular, 
—  the  seeds  often  being  squeezed  together  in  such  a  hit  and 
miss  manner  that  the  number  of  rows  can  only  be  counted 
by  making  cross  sections  of  the  cob.  Experience  with  maize 
cultures  shows  that  there  are  two  distinct  kinds  of  irregularity, 
one  a  physiological  fluctuation  which  is  not  inherited,  and  one 
a  definitely  inherited  character  or  possibly  a  set  of  characters. 
The  non-inherited  fluctuations  are  always  present  while  the 
inherited  irregularity  may  be  present  or  absent.  Th@*  latter 
kind  has  been  isolated  in  several  varieties,  the  most  conspicuous 
being  the  Country  Gentleman  sugar  corn. 

Since  the  inherited  irregularity  can  only  be  distinguished  from 
the  fluctuation  by  breeding  and  then  with  difficulty  owing  to  the 
obscuring  effect  of  the  latter,  it  is  difficult  to  come  to  any  con- 
clusion regarding  the  method  of  its  transmission  when  dealing 
with  mixed  strains.     It  could  undoubtedly  be  determined  by 


132  INHERITANCE   IN   MAIZE. 

careful  work  with  a  cross  of  which  Country  Gentleman  formed 
one  of  the  parents.  We  have  not  made  such  a  cross,  but  obser- 
vations of  large  commercial  cultures  of  Country  Gentleman 
lead  us  to  believe  that  irregularity  is  a  Mendelian  dominant, 
although  it  may  not  act  as  a  simple  mono-hybrid. 

Ears  with  irregular  rows  appearing  in  our  cultures  have  been 
planted  several  times,  but  have  proved  to  have  been  due  ta 
physiological  fluctuation  in  all  but  one  instance.  An  ear  of 
strain  29-2  produced  some  ears  with  irregular  rows,  one  of 
which  happened  to  have  been  inbred.  This  ear  gave  33  normal 
progeny  and  12  with  irregular  rows  in  the  next  generation. 
One  of  these  irregular  ears  gave  33  normal  and  15  irregular 
ears  in  a  further  generation,  while  one  of  the  regular  rowed 
ears  gave  125  normal  and  5  irregular  ears.  One  of  these  5 
irregular  ears  was  selfed  and  will  be  tested  next  year.  This 
is  about  the  percentage  of  irregular  ears  that  the  variety  gives 
in  the  commercial  field,  however,  so  the  idea  suggests  itself, 
that  these  five  ears  were  fluctuations.  If  we  regard  this  as  the 
true  interpretation  of  the  regular  ears  giving  irregular  ears, 
and  reduce  the  number  of  irregularities  in  the  progeny  of  the 
irregular  ears  in  the  same  proportion,  a  ratio  of  66  normal  to  23 
irregular  ears  is  obtained.  This  looks  like  a  case  of  mono- 
hybridism  with  reversed  dominance.  It  is  suggested,  however, 
if  this  is  a  case  of  twice  planting  a  heterozygous  mono-hybrid; 
that  it  is  an  example  of  fluctuating  dominance  in  which  some 
apparently  normal  ears  are  really  heterozygotes.  One  cannot 
even  say  that  only  homozygotes  show  dominance,  for  it  was  an 
irregular  ear  in  each  case  that  threw  normals.  There  is  no 
a  priori  reason  why  this  hypothesis  should  not  be  true,  but  it 
seems  probable  that  a  more  complex  set  of  conditions  exists. 
The  one  fact  that  stands  out  clearly  is  that  if  the  percentage 
of  irregular  ears  increases  much  over  four  percent  in  a  com- 
mercial progeny  row  culture,  the  whole  culture  must  be  dis- 
carded to  eliminate  the  undesirable  "blood." 


Bifurcated  Ears. 

Occasionally  there  is  found  among  the  eight  rowed  flint  corns 
ears  which  have  only  four  rows.  Their  cobs  are  grooved  so  that 
they  appear  to  be  almost  splitting.     One  of  these  individuals 


EARS  WITH  LATERAL  BRANCHES.  133 

appeared  in  a  culture  of  No.  17  (Palmer's  Red-nosed  yellow)  that 
had  been  selfed  for  three  generations.  It  was  grown  with  the 
special  object  of  finding  out  whether  the  four  rowed  condition 
is  a  final  recessive  condition  as  to  number  of  rows.  This  proved 
not  to  be  the  case.  The  condition  is  a  secondary  effect  of  a 
heritable  abnormality  which  causes  the  cob  to  show  various 
conditions  of  splitting  into  two  rowed  sections  at  the  base. 
The  variations  in  this  feature  are  shown  in  Plate  XXIII,  fig.  a. 
From  this  ear,  34  ears  abnormal  in  varying  degrees  and  12  normal 
ears  were  obtained.  This  ratio  suggests  the  progeny  of  an  ear 
heterozygous  for  presence  and  absence  of  the  abnormality. 
It  will  be  tested  further. 

A  bifurcation  of  a  different  kind  appeared  in  the  progeny  of 
No.  7  Leaming  dent  that  had  been  selfed  for  four  years.  In 
its  extreme  form  the  tip  of  the  growing  ear  becomes  monstrously 
fasciate;  but  it  may  vary  toward  the  normal  to  such  a  degree 
that  the  abnormality  is  shown  only  as  a  slight  flattening  of  the 
ear  when  observed  in  cross-section.  The  ear  in  which  this 
abnormality  appeared  was  only  slightly  flattened ;  its  progeny, 
however,  showed  11  with  divided  tip  and  about  20  flattened 
ears  out  of  44.     (See  Plate  X  XII.) 

The  normal-eared  grand  parent  of  No.  7  had  been  crossed  with 
No.  19,  and  from  an  extracted  starchy  ear  of  the  F2  generation 
there  resulted  the  same  abnormality.  This  ear,  No.  (19  x  7)-5-7 
had  a  divided  fasciate  tip.  It  produced  29  ears  with  divided 
tip,  33  ears  abnormally  flattened  and  23  normal  ears,  —  a  ratio 
of  62:  23.  The  illustration  of  this  sort  of  fasciation  shown  in 
Plate  XXII,  fig.  b,  gives  an  idea  of  how  gradually  the  abnormal 
ears  intergrade  with  the  normal  ears.  Yet  this  is  a  dominant 
character  alternatively  inherited.  It  is  difficult  to  tell  the  pure 
normal  ears  by  inspection  but  they  appear  to  breed  true  when 
isolated. 

Ears  with  Lateral  Branches. 

An  illustration  of  an  ear  with  lateral  branches  which  is  prob- 
ably nearer  the  ancestral  type  of  maize  appeared  in  the  original 
culture  of  No.  17.  It  is  figured  in  Plate  X  XIII,  fig.  b.  The  ear 
was  not  hand  pollinated  and  of  course  no  conclusion  can  be 
drawn  from  the  ratio  in  which  the  abnormality  appeared  in 


134  INHERITANCE   IN   MAIZE. 

the  next  generation.  As  a  matter  of  fact  4  ears  out  of  25 
progeny  were  so  affected.  One  of  these  happened  to  have  been 
selfed,  but  it  produced  only  a  few  seeds.  Ten  plants  resulted 
from  this  poor  individual,  two  of  which  were  abnormal. 

The  only  valid  conclusion  from  these  data  is  that  the 
character  does  segregate.  Normals  and  abnormals  are  produced ; 
which  fact  suggests  —  as  stated  earlier  in  the  paper — that  the  loss 
of  the  lateral  branching  character  of  maize  occurred  as  a  retro- 
gressive mutation. 

Plants  with  Striped   Leaves. 

Zea  mays  japonica  is  a  race  which  produces  leaves  with 
longitudinal  stripes  with  and  without  chlorophyll  formation. 
In  other  words,  the  leaves  are  green  with  white  stripes.  Several 
races  of  this  kind  exist  where  the  striping  is  apparently  homozy- 
gous and  the  race  breeds  true.  What  experience  we  have  had 
with  striped  races  has  been  with  another  type  of  striping.  The 
phenomenon  has  appeared  several  times  in  our  cultures,  and  is 
clearly  the  same  thing  that  Baur  ( :  09)  obtained  in  pelargoniums. 
The  full  green  type  is  dominant,  the  striped  type  is  hetero- 
zygous, while  the  homozygous  recessives  are  sometimes  formed 
but  cannot  live  because  they  lack  assimilating  organs.  Crosses 
between  the  striped  plants  and  normal  green  plants  always 
gave  all  green  progeny.  Planting,  in  two  cases,  from  plants 
that  were  striped  when  very  young,  274  normal  and  27  striped 
plants  were  obtained.  This  result  might  seem  to  indicate  a 
more  complex  condition  than  Baur  obtained.  It  is  not  neces- 
sarily so,  however,  for  the  plants  were  first  examined  for  striping 
when  about  18  inches  high.  This  may  have  been  too  late  to 
give  them  the  proper  classification,  since  it  was  found  that  many 
of  the  27  striped  plants  became  greener  as  they  aged.  Several 
plants  without  chlorophyll  died  when  only  a  few  inches  high. 
These  were  probably  homozygous  recessives. 

Hermaphrodite   Flowers. 

Perhaps  it  should  be  mentioned  in  passing  that  the  immature 
sex  organs,  so  called,  of  maize  seem  endowed  with  the  power  of 
becoming  either  stamens  or  carpels.     One  often  finds  a  normal 


HERMAPHRODITE  FLOWERS.  13S 

ear  ending  in  stamens,  and  nearly  every  plant  produces  lateral 
branches  which  have  carpels  and  stamens  mixed  together 
indiscriminately . 

A  number  of  cases  have  also  been  observed  where  a  few  of  the 
ovules  of  an  ear  were  surrounded  by  three  stamens  as  in  a  perfect 
flower.  The  only  instance  we  have  seen  where  all  of  the  ovules 
had  three  stamens  within  the  glumes  of  the  flower  that  is  usually 
aborted,  was  that  of  the  dwarfs  with  wide  leaves  mentioned 
under  the  heading  "Dwarf  forms."  It  might  be  supposed  that 
this  was  an  atavistic  type  representing  some  of  the  characters, 
at  least,  of  the  ancestral  maize.  We  should  prefer  to  believe, 
however,  that  this  development  of  stamens  is  merely  an  accom- 
paniment of  the  dwarfing  due  to  an  endeavor  to  retain  physio- 
logic balance.  That  is,  this  type  is  really  a  healthy  luxuriant 
form  producing  very  large  ears  for  such  a  small  plant.  There 
may  have  been  developmental  energy  present  which  when 
unable  through  inner  limitations  to  produce  a  tall  plant,  mani- 
fested itself  in  producing  stamens. 

Considered  together,  these  various  abnormalities  present 
several  interesting  features.  It  would  be  rash  to  make  any 
dogmatic  statements  in  regard  to  their  inheritance,  yet  it  is 
fair  to  say  that  if  dominance  shows  progressive  —  and  recessive- 
ness  retrogressive  — ■  variations,  both  types  are  present.  Some 
of  them  are  evidently  simple  in  character  —  as  far  as  inheritance 
goes  —  while  others  are  complex.  It  may  be  that  the  same 
apparent  type  of  variation  will  be  found  to  be  simple  in  some 
races  and  complex  in  others.  By  this  it  is  meant  that  both 
3  :  1  and  higher  ratios  will  be  found  affecting  characters  which 
to  the  eye  are  the  same. 

It  does  not  seem  probable  that  abnormal  and  degenerate  types 
are  always  or  even  commonly  extracted  recessives  in  which 
absence  of  characters  is  concerned,  as  Davenport  ( :  08)  has 
suggested.  This  statement  has  little  basis  from  the  data  pre- 
sented here,  but  the  senior  author  has  worked  out  certain 
dominant  abnormal  types  in  the  genus  Nicotiana  which  adds 
to  our  experience.  The  presumption  is  that  they  are  more 
often  dominant  like  most  of  the  abnormalities  found  in  man. 

Perhaps  the  fact  of  prime  importance  from  these  data  is  the 

,  variable    dominance    of    characters    and    their    obscuration    by 

physiological   fluctuation.     As   stated   once   before,  this   shows 


136  INHERITANCE   IN   MAIZE. 

the  extreme  importance  of  pedigree  cultures  to  the  commercial 
breeder,  for  some  of  these  complex  abnormalities  cannot  be 
distinguished  from  normal  plants  by  gross  inspection.  It  is 
possible  that  histological  study  might  show  points  of  difference 
but  these  methods  are  not  at  the  command  of  the  commercial 
grower. 

It  will  be  noticed  that  several  monstrous  variations  occurred 
in  strains  that  had  been  selfed  for  several  generations.  The 
effects  of  inbreeding  in  maize  will  form  the  subject  matter  of 
another  paper,  but  it  might  be  well  to  suggest  here  a  possible 
cause  for  their  production.  Inbreeding  in  maize  gives  the  same 
effect  as  lack  of  nutrients,  while  cross-breeding  gives  the  opposite 
effect.  There  is  retardation  or  acceleration  of  cell  division, 
respectively.  Now  such  monstrosities  as  ears  with  divided 
tips,  occur  more  frequently  either  in  cross-bred  plants  that 
are  over  supplied  with  fertility,  or  in  inbred  plants.  Perhaps 
the  first  case  represents  fluctuation  only,  and  is  unlnherited; 
as  to  this  point  we  have  no  data.  But  disregarding  this  pos- 
sibility, might  not  abnormal  distribution  of  chromatin  produce 
these  variations  in  both  cases.  The  first  kind  could  be  caused 
by  abnormally  accelerated  division  and  the  second  kind  b}- 
abnormally  retarded  division. 

General  Conclusions. 

The  various  points  of  genetic  theor}^  discussed  in  this  paper 
are  not  sufficiently  connected  to  make  possible  a  short  and  at  the 
same  time  intelligible  recapitulation.  We  simply  desire  to 
mention  our  conclusions  regarding  the  central  problem  of  all 
genetic  investigations,  that  of  laws  of  heredity. 

When  Mendel's  Law  of  Heredity  was  rediscovered  in  1900,  it 
was  the  general  belief  that  it  covered  only  a  few  isolated  cases. 
Many  apparent  exceptions  were  cited.  One  by  one,  however, 
these  exceptions  have  been  found  to  yield  to  interpretation  by 
simple  extensions  of  the  Mendelian  notation  when  fully  under- 
stood. In  our  experience  as  reported  here,  no  exceptions  to 
Mendelian  interpretation  have  been  found.  Such  exceptions 
may  exist,  yet  it  seems  as  unwise  to  say  that  Mendel's  Law  is 
not  general  as  to  conclude  at  once  that  it  can  be  made  to  cover 
every  possible  case.      One  may  say  that   Mendel's  Law  has 


PLATE    XXIII. 


Jj#^i#*l«Si-.^*^*^ 


a.     Heteroz\-gous  bifurcated  cob  above;   dominant  and  heterozygous  pro- 
geny below  showing  imperfect  dominance. 


b.     Multiple   ear.     An   imperfectly  dominant  character.     Aboriginal  maize 
probabh'  possessed   a  similar   character. 

Abnormalities. 


PLATE    XXIV. 


^ t j: ^ 


A   plant  of   the  dwarf   mutation   appearing  in   Stowell's    evergreen   sugar 
maize  compared  with  a  normal  ear  of  the  latter. 


Dwarf  Forms. 


PLATE    XXV. 


A  dwarf  type  which  appeared  in  Learning  dent  maize  compared  with  a 
normal   ear   of   that  variety. 


Dwarf  Forms. 


CONCLUSIONS.  137 

covered  so  many  cases  that  its  generality  is  rendered  highly 
probable,  although  insufficient  genetic  investigation  has  been 
accomplished  to  place  it  on  equal  terms  with  any  of  the  great 
laws  of  physics  and  chemistry.  Yet  some  of  the  great  laws 
of  chemistry  were  accepted  when  surrounded  by  seeming 
exceptions.  Some  of  these  exceptions  have  been  cleared  up 
by  such  recent  advances  as  the  Ionic  Theory  and  the  Phase 
Rule;  some  still  remain. 

Is  it  not  probable  that  other  like  generalities  will  be  found 
in  biology,  which,  although  they  may  entirely  change  our  general 
conception  of  the  fundamental  action  of  Mendel's  Laws,  will 
nevertheless  leave  the  facts  upon  which  it  was  based  as  useful 
and  practicable  as  have  been  left  the  facts  of  chemical  recombi- 
nation in  definite  and  multiple  proportions  in  the  light  of  the 
Electron  Theory  ? 


138  INHERITANCE  IN   MAIZE. 


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